Electrical Power Production Apprentice Study Guide/Workbook (SW) - February 2024 PDF

CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR STUDY GUIDE/WORKBOOK (SW) J3ABR3E032 00AD-VII TECHNICAL TRAIN...

CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR STUDY GUIDE/WORKBOOK (SW) J3ABR3E032 00AD-VII TECHNICAL TRAINING Electrical Power Production Apprentice Block VII - Troubleshooting February 2024 782 TRAINING GROUP 366 TRAINING SQUADRON Sheppard AFB TX 76311 THIS DOCUMENT CONTAINS COPYRIGHTED MATERIAL. Copyright release is on file in the electronic course record set. Foreign Disclosure: This information is furnished on the condition that it will be given substantially the same degree of security protection given to it by the United States and will not be released to another nation without United States Air Force authorization. This briefing, presentation, or document is for information only. No U.S. Government commitment to sell, loan, lease, co-develop or co-produce defense articles or provide defense services is implied or intended. DESIGNED FOR AETC COURSE USE NOT INTENDED FOR USE ON THE JOB OPR: 366 TRS/TRR CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR THIS PAGE INTENTIONALLY LEFT BLANK  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR PURPOSE OF STUDY GUIDE/WORKBOOK This Study Guide/Workbook (SW), along with classroom presentations will provide the necessary information for satisfactory completion of this block of instruction. It has been designed to ease understanding of subject matter presented throughout this block. The SW includes practical work assignments and exercises in conjunction with study assignments for each unit of instruction. You are to complete all assignments as you progress through each unit. The use of a trade named manufacturer’s product, commodity or service in this publication does not imply endorsement by the United States Air Force. TABLE OF CONTENTS UNIT 1. ENGINE SYSTEMS........................................................................................................... 1-1 UNIT 2. ELECTRICAL SYSTEMS.................................................................................................. 2-1 UNIT 3. BATTERY CHARGERS.................................................................................................... 3-1 UNIT 4. INSPECT, TEST AND REPLACE RECTIFIER ASSEMBLY......................................... 4-1 BIBLIOGRAPHY.................................................................................................................................. A Supersedes J3ABR3E032 00AD, 01 March 2023 i CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR THIS PAGE INTENTIONALLY LEFT BLANK  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-1 SW J3ABR3E032 00AD III UNIT 1. ENGINE SYSTEMS OBJECTIVES: a. Without reference, identify basic facts and terms related to engine malfunctions with at least 80% accuracy. b. Given TO 35C2-3-444-12, determine procedures for troubleshooting mobile generator engine systems with at least 75% accuracy per system. INTRODUCTION Engine malfunctions are something a Power Production technician will encounter during their time in this career field. Identifying what the malfunction is and what engine sub-system the malfunction is coming from will save time and resources in troubleshooting. ENGINE MALFUNCTIONS OBJECTIVE: 1a. Without reference, identify basic facts and terms related to engine malfunctions with at least 80% accuracy. INFORMATION In this section, several different engine malfunctions are discussed. This textbook is meant to serve as a general guideline for troubleshooting and should not be used as a primary means for troubleshooting. Always refer to the manufacturer’s manuals, or appropriate technical order, for equipment specific procedures and troubleshooting. DIESEL/GASOLINE ENGINE SYSTEM MALFUNCTIONS Diesel and gasoline share some common mechanical engine malfunctions. Both work similar in function, apart from fuel delivery and combustion techniques. Fuel System Malfunctions Engines failing to start can be a common symptom of a fuel system malfunction in either gas or diesel engines. Common causes can be an insufficient fuel supply, degradation of fuel lines, failing tank conditions, and poor fuel quality. Cooling System Malfunctions Problems in the cooling system will show symptoms such as high coolant temperature and low coolant temperature. The cause of high coolant temperature can be the result of coolant loss, which can be observed by the level in the surge tank. Low temperature, however, is commonly caused by a thermostat stuck in the open position. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-2 SW J3ABR3E032 00AD III Lubricating System Malfunctions The lubricating system can exhibit symptoms of malfunctions to include low oil pressure, and high oil pressure. Either of these symptoms can be a result of a dirty or clogged oil filter or insufficient oil levels. Intake and Exhaust System Malfunctions Malfunctions in the intake or exhaust are numerous in both gas and diesel engines. Symptoms include low power output and irregular exhaust color. Low power output, or power loss, can be the cause of dirty clogged air filter or muffler, a leak in the exhaust system, or internal engine malfunction. Irregular exhaust colors can indicate burning coolant if white smoke, burning oil if blue/gray smoke, and black smoke could indicate an improper fuel/air ratio. DIESEL ENGINE SYSTEM MALFUNCTIONS Fuel System Diesel and gasoline fuel systems can have similar symptoms, but the causes of these symptoms can be extremely different between the two. An engine that runs erratic or misfires in a diesel may be caused by excessive carbon buildup in the turbocharger or leaks in the charge piping from the turbocharger. A diesel that exhibits excessive black exhaust smoke can be the result of the same causes above plus problems in the cylinder head, such as valves clogging, or a faulty injection pump. Intake and Exhaust System The intake and exhaust systems in diesel engines show symptoms that do not arise in gasoline engines. GASOLINE ENGINE SYSTEM MALFUNCTIONS Ignition System The ignition system must be capable of producing electrical current across the spark plug gap. Any problem with the ignition system’s ability to deliver high voltage to the spark plug would result in the engine failing to start because of no spark or some cylinders misfiring due to weak (or no) spark to those cylinders. Fuel System There may be times when gasoline engines will miss under load, lack power, or backfire through the carburetor. Gasoline and air mixture igniting inside the intake manifold by a flame from the cylinder causes backfiring. Detonation occurs when the air-fuel mixture in the cylinder ignites before the spark plug ignites it. Causes could be from the spark plug center electrode getting too hot (overheated) or an excessive CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-3 SW J3ABR3E032 00AD III carbon build-up in the cylinder caused by running an engine too rich. A pinging sound could mean pre-ignition is occurring. The main difference is at what point the event occurs and the sound they can make. Detonation occurs after the compression stroke. During detonation, the fuel explodes rather than burning smoothly. This explosion puts much more force on the piston, increases temperatures and increases noise. Intake and Exhaust System A gasoline engine’s intake and exhaust systems can differ from a diesel engine. If the gasoline engine is equipped with a carburetor. a carburetor’s idle adjust screw could be out of adjustment so the engine might not start or have erratic engine speed if it does start. In cold environments, a damaged choke plate could lead to the engine starting problems. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-4 SW J3ABR3E032 00AD III Complete Workbook Exercise 1a. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 1a: Engine Malfunctions REFERENCE: SW J3ABR3E032 00AD-VII, lecture notes INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your response to the questions/statements that follow. 1. The common problem of failing to start between gas and diesel engine fuel systems are caused by what? 2. In a gas and diesel engine’s cooling systems, what can cause an engine to have a high coolant temperature? 3. In a gas and diesel engine’s cooling system a _____________stuck in an open position will prevent the engine from warming to operating temperature. 4. What causes excessive black smoke in a diesel engine? 5. __________ occurs when the air-fuel mixture in the cylinder ignites before the spark plug ignites it from the ignition event. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-5 SW J3ABR3E032 00AD III OBJECTIVES b. Given TO 35C2-3-444-12, determine procedures for troubleshooting mobile generator engine systems with at least 75% accuracy per system. INTRODUCTION As equipment is used, parts will break and wear out. As this happens, which parts wear out may not be obvious from its symptoms. Learning to troubleshoot not only speeds up the process of bringing equipment back in service but also increases the technician’s knowledge of the equipment. Objective: 1b. Given TO 35C2-3-444-12, determine procedures for troubleshooting mobile generator engine systems with at least 75% accuracy per system. INFORMATION TROUBLESHOOTING Troubleshooting provides a systematic approach of analyzing, locating and correcting malfunctions. The problem may be familiar to the technician and is often the result of normal wear and tear. The symptoms may also require the technician to understand theory of operation and reference technical publications and charts to troubleshoot a malfunction. SAFETY PRECAUTIONS When operating or troubleshooting any type of equipment, safety should the highest priority. Strictly adhere to Technical Order (T.O.) or manufacturer’s manual guidance is essential. Pay close attention to all T.O. NOTES, WARNINGS, and CAUTIONS and employ Risk Management (RM) principles throughout every task. In addition to using the T.O. and practicing RM, each member of a troubleshooting team should comply with the following: Personnel will remove all jewelry prior to entering the work site. Wear the proper PPE for the task being undertaken. Keep hands away from hot components and moving machinery. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-6 SW J3ABR3E032 00AD III INTRODUCTION TO TROUBLESHOOTING CHARTS Two Primary References - Two primary references found in the T.O. apply to troubleshooting engine systems: troubleshooting charts and system and circuit descriptions. Troubleshooting Chart (Figure 1-1) consists of a specific malfunction, probable causes, and recommended actions to correct the malfunction. Troubleshooting charts are found in the T.O. or manufacturer’s manual for the equipment. The charts are not all inclusive to all possible problems but will provide a list of common malfunctions. System and Circuit Descriptions (Figure 1-2) is the text within the T.O. or manufacturer’s manual providing detailed explanations on system and component operations. Consult this information when working or troubleshooting problems. Figure 1-1: Troubleshooting Chart Engine starting is accomplished primarily with two 12-volt batteries, connected in series to provide 24. VDC power, and a starter. The starter includes a cranking motor and a solenoid. To permit engine starting, the DC CONTROL POWER circuit breaker must be pushed in, the DEAD CRANK switch must be in the NORMAL position, and the BATTLE SHORT switch must be in the OFF position. In addition, any ENGINE SHUTDOWN fault previously registered on the CIM display screen must have been corrected by activating the FAULT RESET switch. When the ENGINE CONTROL switch is placed in the START position, the starting circuits supply 24 VDC power to the starter. As the engine accelerates to approximately 900 RPM, the DCS speed control unit disconnects power from the starter. Figure 1-2: System and Circuit Descriptions CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-7 SW J3ABR3E032 00AD III TROUBLESHOOTING PROCEDURES An efficient troubleshooter follows certain steps to quickly find the problem as well as reference all supporting manuals for the equipment. The fundamental steps below will guide any form of troubleshooting, mechanical or electrical: Perform an operational check. Analyze the malfunction. Locate the malfunction. Perform corrective action. Perform a follow-up operational check. To troubleshoot effectively, follow a systematic procedure. First, study the symptoms of the trouble thoroughly and ask these questions: 1. What were the warning signs preceding the trouble? 2. What recent repairs have been completed? 3. Has a similar trouble occurred before? Perform an Operational Check The first step is to perform an operational check of the generator to determine if an actual trouble really exists. In starting and operating any generator set, T.O.s or manufacturer’s manuals prescribe certain checks and procedures to prevent engine and generator malfunctions or damage. Proper inspections and correct operating procedures solidify efficient operation and extend the life of the equipment. Improper inspections and incorrect operating procedures could cause faults, inefficient operation, and possible damage or destruction to equipment. Follow the step-by-step procedures in the T.O. for the equipment item. A thorough visual inspection of all components often reveals minor discrepancies that can be corrected and prevent major problems from occurring. Analyze the Malfunction The second step is to analyze the malfunction. Detect the trouble by using your senses of sight, sound, smell, or touch. Power Production technicians have many instruments installed on the generator to indicate malfunctions, however, in some cases, the instruments will not indicate a malfunction. Some malfunctions may be detected by sound, such as a vibration of a generator component. Never accept another technician’s word pertaining to a malfunction. Technicians should use their own senses in analyzing the malfunction themselves. Once aware of a malfunction, consult the proper technical manual for normal equipment operation. This helps to get a clearer picture of how the circuit involved should be working normally. If available, check the troubleshooting chart in the manual for probable causes and remedies. This step may reduce the process to a few simple checks. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-8 SW J3ABR3E032 00AD III If the troubleshooting chart proves to be of no help, use the system description to determine possible malfunctions associated with this issue. Identifying the components involved in a system can aid in making a list of possible faulty parts. Locate the Malfunction Once the malfunction has been determined, perform the various checks as outlined in the T.O./manufacturer’s manual. Locating the cause of a malfunction may be the most difficult part since it requires operational knowledge of the system. Some faults may require the performance of certain tasks before testing. Perform Corrective Action After locating the cause of the malfunction, a professional and permanent repair must be performed. Careless repairs will only worsen a situation. Use approved replacement parts and not something “created in-house.” Perform a Follow-up Operational Check Performing a follow-up operational check after repairs proves the completed work is effective and fixed the malfunction. Another fault may remain within the equipment and only one symptom of the malfunction may have been remedied. The operational check is the most crucial step in troubleshooting! TROUBLESHOOTING DIESEL ENGINE SYSTEMS Common malfunctions were discussed in a previous block. As a review, some are listed below. T.O.s or the manufacturer's manual will be used to provide guidance on correcting any malfunction. Lubricating System Common malfunctions include high/low oil pressure, dirty filtration and/or clogged oil filters. Solutions may be as simple as checking and adjusting the oil level or as complex as replacing main shaft bearings. Cooling System Common malfunctions include coolant loss and high/low temperature. Corrective actions can be as simple as verifying an adjusting coolant level but may involve component replacement, i.e. a thermostat or radiator. Intake and Exhaust Systems Common malfunctions are low power output, excessive exhaust, excessive exhaust temperatures, exhaust valves stuck open, leaks in the exhaust system, and clogged mufflers. Cleaning or replacing air filter elements may correct symptoms of difficulty starting, excessive black smoke from the exhaust and erratic engine operation. A clogged muffler may cause back pressure in the engine; the CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-9 SW J3ABR3E032 00AD III technician could tighten the exhaust piping connects or replace the manifold gaskets and bolts. Finally, adjusting the intake and exhaust valves can correct erratic engine speed. Diesel Fuel Systems Specific For a diesel engine to operate, the correct amount of fuel must be injected into the combustion chamber, at the correct time. A problem in the fuel system will affect the operation of the engine. Fuel system problems may prevent the engine from starting, cause erratic operation or misfires and emit excessive black exhaust smoke; even though, the engine will not be overloaded. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 1-10 SW J3ABR3E032 00AD III Complete Workbook Exercise 1b. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 1b: Troubleshooting Engine Systems. REFERENCE: SW J3ABR3E032 00AD-VII, Lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your responses to the questions/statements that follow. 1. Troubleshooting is a ____________________ of analyzing, locating and correcting malfunctions. 2. What should be your highest priority when operating and troubleshooting any type of generation equipment? 3. What are two types of references included in the T.O./manufacturer’s manual that assist in troubleshooting engine systems? 4. What are the fundamental steps of complex troubleshooting? 5. During which step in the troubleshooting process do you create a short list of things to check? 6. Why is an operational check performed following corrective action? 7. List three common malfunctions associated with the lubricating system. a. ______________ b. ______________ c. ______________ 8. List three common malfunctions associated with the intake and exhaust system? a. ______________ b. ______________ c. ______________ CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-1 SW J3ABR3E032 00AD-VII UNIT 2. ELECTRICAL SYSTEMS OBJECTIVES: a. Without reference, identify basic facts and terms related to types of wiring diagrams with at least 75% accuracy. b. Given electrical wiring diagrams and working as a team, troubleshoot a DC electrical system with no more than two instructor assists per task. c. Given TO 35C2-3-444-12 and working as a team, adjust the set points and troubleshoot an electronic governing system with no more than two instructor assists. INTRODUCTION Electrical testing is instrumental in correcting malfunctions. If a technician cannot read diagrams and use test equipment, they will not be able to identify faulty components and replace them. The basic and most used diagrams and test equipment is discussed and is used during this unit. WIRING DIAGRAMS OBJECTIVE: 2a. Without reference, identify basic facts and terms related to types of wiring diagrams with at least 75% accuracy. INFORMATION PURPOSE OF ELECTRICAL DIAGRAMS Electrical diagrams provide the “road maps” through electrical circuitry. They are essential to learn circuit operations and isolate problems during troubleshooting. Wiring diagrams will not be drawn to scale and are the first thing an engineer draws. The engineer designs the electrical diagram to identify components and positioning. Diagrams aid in troubleshooting and allow for understanding of the circuit’s operation. They show circuit components, the path of current flow, and the electrical connections between the circuits. Electrical diagrams have a threefold purpose: (1) they show system components, (2) allow for understanding of system operation, and (3) used as an aid in troubleshooting electrical systems. The first step to understanding electrical diagrams, know which components can be found in the circuit and how they operate. The best place to find this information will either be a technical order or manufacturer’s manual. The most important "key" to reading and understanding electrical diagrams is the technician’s ability to interpret symbols. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-2 SW J3ABR3E032 00AD-VII SYMBOLS Symbols is the “language” of diagrams. To be able to read a diagram requires understanding the language. Knowledge of electrical symbols allows for installation of circuits, tracing circuits, and locating malfunctions. Figure 2-1 provides typical symbols used to identify circuit components. These represent a few examples of different types used on electrical diagrams. Figure 2-1: Electrical Symbols The symbols found in various T.O.s and manufacturer’s manuals may differ and should be interpreted as designated. Engineers often use abbreviations to save space when writing diagrams. Between the abbreviations and symbols, electrical diagrams tell the story of the circuitry. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-3 SW J3ABR3E032 00AD-VII TYPES AND USES OF DIAGRAMS Electrical diagrams differ in the information provided to the technicians. Some is more useful than others, but all serving their own purpose. The four electrical diagrams most used are one-line, schematic, connection, and interconnection diagrams. One-line Diagram The one-line diagram, also called a single-line, is the most basic diagram used. This diagram helps maintain continuity in the process of extracting circuits. It conveys basic information about the operation of a circuit or a system of circuits but omits much of the detailed information found in a schematic or connection diagram. This diagram allows the technician to see a simplified diagram of a complex circuit by using single lines for multi-conductor circuits. A single line is used to show either AC or DC circuits with thicker lines representing primary circuits and medium lines for secondary circuits. Small circles normally portray relays and meters, and small rectangles for resistors, transfer switches and selector switches. All circuit devices are designated with their functions, while meters and switches are abbreviated. A typical one-line diagram can be found in figure 2-2. Figure 2-2: Typical One-line Diagram CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-4 SW J3ABR3E032 00AD-VII Schematic Diagram The schematic diagram (or elementary) is the most important and useful for troubleshooting and extracting circuits. Figure 2-3 is an example of a schematic diagram. Schematic diagrams show all circuit components, without regard for physical location, and is the simplest form of diagram. It gives an overall view of a particular system, shows circuit operation, and shows where the functions occur in an exact Figure 2-3: Typical Schematic Diagram sequence. The schematic diagram allows tracing the affected circuit, and usually includes elements such as solenoids, relays, contacts, meters, and mechanical linkages. The schematic diagram also contains a legend; typically found at either the bottom or bottom right corner of the schematic. Some schematics do not have internal conductor numbers but do contain connections for all contacts numbered. Connection Diagram The connection diagram, also called a wiring diagram, shows all electrical connections of an installation, or component devices and equipment. Commonly referred to as an “As Built” diagram, the location of the devices on the diagram is relative to the locations of those devices on the equipment, as seen from the rear of a panel. The terminal numbers of the devices can be identified aiding with conductor tracing. Use the connection diagram in conjunction with the schematic diagram for extracting specific circuits during the troubleshooting process. Examining the connection diagram in figure 2-4 (next page), it is impractical to show all the wiring on a diagram. Connection diagrams provide the complete conductor numbers and the plug and jack pin numbers necessary to completely extract and troubleshoot specific circuits. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-5 SW J3ABR3E032 00AD-VII Figure 2-4: Connection Diagram Interconnection Diagrams Interconnection diagram (Figure 2-5) shows complete connections between equipment units, unit assemblies, and associated systems. Interconnection diagrams also show the connection of components inside the panel, as viewed from the rear, in their relative positions and determine the arrangement of conduits. Normally omitted from the interconnection diagram is the internal connections of units or unit assemblies. Thicker lines are the exciter, field circuits by medium lines and the smaller wiring by light lines normally show the main power circuits. Dot-dash lines outline the panel sections. Figure 2-5: Interconnection Diagram CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-6 SW J3ABR3E032 00AD-VII Complete Workbook Exercise 2a. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 2a: Wiring Diagrams REFERENCE: SW J3ABR3E032 00AD-VII, lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your response to the questions/statements that follow. 1. What is the connection diagram also called? 2. What is considered the language in electrical diagrams? 3. Which electrical diagram is considered the most important? 4. What is normally omitted in connection diagrams? CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-7 SW J3ABR3E032 00AD-VII INTRODUCTION Electrical components can malfunction just as likely as mechanical components. Troubleshooting electrical components follows similar steps and requires the use of TOs or manufacturer’s manuals. TROUBLESHOOT DC ELECTRICAL SYSTEMS OBJECTIVE: 2b. Given electrical wiring diagrams and working as a team, troubleshoot a DC electrical system with no more than two instructor assists per task. INFORMATION PURPOSE OF A WIRING DIARGRAM As a review, electrical diagrams (also known as wiring diagrams) provide the “road map” of the electrical circuits. Diagrams aid in troubleshooting and allow for understanding of the circuit’s operation, showing circuit components, the path of current flow and the electrical connections between the circuits. SYMBOLOGY Symbols provide the “language” of diagrams. The ability to read a diagram requires understanding the language. Knowledge of electrical symbols allows for installation of circuits, tracing circuits, and locating malfunctions. Commonly used symbols include the following: Motors –B Solenoid – L Capacitor - C Meter - M Circuit Breaker – CB Resistor – R Light – DS Switch – S Fuse – F Transformer - T Alternator - G Terminal Board – TB Ground – GND Battery - BT Relay – K Legends Legends identify device numbers and abbreviations in the drawing. Without a legend to identify components, some wire diagrams would be very difficult to interpret. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-8 SW J3ABR3E032 00AD-VII TYPES AND USES OF DIAGRAMS Four types of wiring diagrams used in troubleshooting include one-line, schematic, connection, and interconnection diagrams. One-line Diagram One-line diagrams provide an instant overview of the system and often referred to as a loop diagram. This diagram is the most basic diagram with main circuits illustrated with thick lines and secondary circuits with thin lines. One-line diagrams do not show the internal wiring connections of devices. (Figure 2-6) Figure 2-6: One Line Diagram CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-9 SW J3ABR3E032 00AD-VII Schematic Diagram Schematic diagrams are the most useful for troubleshooting. These diagrams show all circuit components in a straight line without regard for physical location and the sequence of events for circuit operation. All schematic diagrams contain a legend. (Figure 2-7) Figure 2-7: Schematic Diagram CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-10 SW J3ABR3E032 00AD-VII Connection Diagram (Troubleshooting) A connection diagram shows all electrical connections of an installation or component devices and equipment. Commonly referred to the “As Built diagram. The diagram shows the location of the devices relative to the locations of those devices on the equipment, often seen from the rear of a panel or device. Use the connection diagram, in conjunction with the schematic diagram, for extracting specific circuits during the troubleshooting process. (Figure 2-8) Figure 2-8: Connection Diagram Connection diagrams provide the following: 1. Wire number scheme a. Composed of a set of numbers and letters (i.e., 165E). i. Three-digit number designator is used to identify the type of circuit, i.e., AC, DC, or ground. ii. A letter designates progression and aids in tracing and extracting circuits, i.e. “A” is closest to the batteries/alternator. The wiring scheme noted above is for the MEP-806A. Other generator manufacturers will have their own unique wire identification system. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-11 SW J3ABR3E032 00AD-VII 2. Connector Plugs a. Multi-wire, quick disconnect, pin and jack system. b. “P” represents the pin side of the connector (Figure 2-9). c. “J” represents the jack side of the connector (Figure 2-10). Figure 2-9: “P” Connector Figure 2-10: “J” Connector d. Various triangles with letters on electrical wiring diagrams represent the jacks on the J3 Diagnostic Plug (Figure 2-11) used for voltage and continuity checks during troubleshooting. Figure 2-11: J3 Diagnostic Plug CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-12 SW J3ABR3E032 00AD-VII 3. Terminal Boards (Figure 2-12) a. Provide connection points for circuits components. b. Each terminal is given a number or letter for identification. c. Exercise extreme caution while generator is running. AC voltage may be present. Figure 2-12: Terminal Board Interconnection Diagrams Interconnection diagrams show complete connections between equipment units, unit assemblies, and associated systems. They also show the connection of components inside the panel as viewed from the rear of their relative positions and can be used to determine the arrangement of conduits. Internal connections of units or unit assemblies are often omitted. Heavy lines identify main power circuits, medium lines identify the field circuits, and light lines identify the smaller wiring. Dot-dash lines outline the panel sections. (Figure 2-13) Figure 2-13: Interconnection Diagram TRACING CIRCUITS Tracing circuits involves isolating a specific circuit from a diagram or diagram set. Isolating the circuit aids in troubleshooting the electrical malfunction and allows the circuit to be properly tested. Follow the circuit operation explanation in the appropriate T.O. or manufacturer's manual and trace the circuit on the schematic diagram. While tracing, color-code the circuit to allow for easy identification and a clear understanding of a particular circuit. When tracing circuits on a diagram, use the rules in the section below: CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-13 SW J3ABR3E032 00AD-VII Rules of Tracing Circuits RULE 1 - Consult the appropriate technical reference for circuit information. The text within the reference will give a description of all major system functions. The information is written to help the technician understand circuit operation. The circuit information will include how each component operates, identifies the power source and main units of resistance, and current flow in the circuit. RULE 2 - Make a list of the circuit components, identifying them as read from the technical reference. This aids in locating circuit components prior to tracing the circuit on the diagram. RULE 3 - Identify components on schematic diagram. Once the list of components has been established, identify them on the wiring diagram by circling or highlighting the component. With each component marked, the tracing process will become easier to trace in the next step. RULE 4 - Locate and trace the main unit of resistance back to the power source. The "main unit of resistance" refers to the specific circuit component necessary to be powered for the circuit to energize. Normally, the circuit's name identifies the "main unit of resistance"; i.e. The crank circuit's main unit of resistance is the start motor. Complete the circuit by tracing the wiring back to the power source on both the positive (+) and negative (-) sides of the main unit of resistance. RULE 5 – While tracing, note the position of all switches from the wiring diagram's legend and set the switches in the proper position. Eventually, when tracing the positive or negative circuits, trace up to normally open switches or relay contacts. Set switches and relay contacts into the operational position to maintain the circuit's continuity back to the power source. By doing this, coils of the relays will energize, controlling the contacts. Remember, wiring diagrams show all switches, contacts, relays, and other electrical devices in the normal or “de-energized” position. The exception to this would be if otherwise specified. The question now will be, how to set the contacts to the proper position? To do this, treat the coil of the relay as the main unit of resistance until closing the contacts controlled by that relay. Trace the negative (-) side of the coil wiring back to the negative (-) side of the power source. Then, trace the positive (+) circuit of the relay back to the positive (+) side of the power source. Tracing the relays circuit back to the power source “energizes” the relay. This “closes” the normally open relay contacts. After “closing” the relay contacts, continue tracing the original circuit back to the power source. Repeat this process every time encountering an open relay contact. Tracing the circuit simplifies circuit extraction because a traced circuit has every component, wire, and test point clearly identified. Additionally, the troubleshooter will need to trace the specific circuit on the connection “Troubleshooting” diagram. Tracing the circuit on the connection diagram facilitates circuit extraction. Use the schematic diagram to guide through the circuit on the connection diagram. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-14 SW J3ABR3E032 00AD-VII Circuit Tracing Example: Start Circuit RULE 1: Consult appropriate technical reference as seen in figure 2-14. Engine starting is accomplished primarily with two 12-volt batteries, connected in series to provide 24 VDC power, and a starter. The starter includes a cranking motor and a solenoid. To permit engine starting, the DC CONTROL POWER circuit breaker must be pushed in, the DEAD CRANK switch must be in the NORMAL position and the BATTLE SHORT switch must be in the OFF position. In addition, any ENGINE SHUTDOWN fault previously registered on the malfunction indicator panel must have been corrected and the malfunction indicator panel must have been reset. When the MASTER SWITCH is then placed in the START position, the starting circuits supply 24 VDC power to the starter. As the engine accelerates to approximately 900 rpm, the starting circuits disconnect power from the starter. When the MASTER SWITCH is first moved to the START position, the various instrument and control circuits are energized. The Engine Starting System includes two control circuits. One starting control circuit energizes the start relay through closed switch contacts of the engine fault relay and the BATTLE SHORT circuit. The other starting control circuit energizes the cranking relay coil through closed contacts of the crank disconnect switch and the start relay. (The crank disconnect switch is an integral part of the electronic governor control.) With the cranking relay energized, power passes from the batteries through closed contacts of the cranking relay to energize the starter solenoid. With the starter solenoid energized, power passes from the starter solenoid to the cranking motor. The cranking motor then cranks the engine. Engine speed is sensed by the magnetic pickup which sends a signal to the electronic governor control. As the engine accelerates to approximately 900 rpms, the signal from the magnetic pickup causes the crank disconnect switch to open one set of contacts and close another set of contacts. The open contacts break the circuit to the cranking relay and stop engine cranking. The closed contacts cause the field flash relay to be energized. When the MASTER SWITCH is moved to one of the two RUN positions, both starting control circuits are deenergized. The other generator set control and instrument circuits remain energized. Figure 2-14: Circuit Description CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-15 SW J3ABR3E032 00AD-VII RULE 2: Make a list of circuit components. The components required to start a MEP 806A engine (flow chart (Figure 2-14.1) located in T.O.) include Batteries (BT1 & BT2), Dead Crank Switch (S10), Emergency Stop Switch (S17), DC Control Power Circuit Breaker (CB1), Master Switch (S1), Engine Fault Relay (K12), Battle Short Switch (S7), Crank Disconnect Switch (S14), Start Relay (K15), Cranking Relay (K2), Starter Solenoid (L4), Cranking Motor (B1), and Magnetic Pickup (MPU). Figure 2-14.1: Engine Start Flow Chart CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-16 SW J3ABR3E032 00AD-VII RULE 3: Identify the components on the schematic diagram (Figure 2-15). Figure 2-15: Component Identification CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-17 SW J3ABR3E032 00AD-VII RULE 4: Locate and trace the main unit of resistance back to the power source (Figure 2-16). Figure 2-16: Schematic with Traced Branches CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-18 SW J3ABR3E032 00AD-VII EXTRACTING CIRCUITS During the troubleshooting process, it may be easier to extract only the specific circuit. Instead of navigating an entire wiring diagram, the technician can simplify the circuit by creating a drawing just for the circuit affected. With each circuit, the path must first be known. Since the circuit has been traced on the schematic diagram, the following guidelines will aid in drawing an extraction from the schematic and connection diagrams. Using the schematic diagram as a guide, extract the circuit from the connection diagram. The schematic diagram is important because it is your guide through the connection diagram. The schematic shows where you are, where you are going, and where you came from. When one of these factors is not known, extraction of complex circuits becomes almost impossible. Extracted circuits must identify and label all circuit components. These components include coils, relays, light bulbs, wires/wire numbers, connector points, terminal boards, Cannon plugs®, and switches and contacts, and contact positions (normally open/NO or normally closed/NC). When extractions have been created properly, additional reference will not be required to troubleshoot the circuit. Begin by locating the main unit of resistance on both the schematic and connection diagrams. Record the device name on the extraction while leaving enough room to add all other required components (i.e., coils, relays, light bulbs), connection points, terminal boards, Cannon plugs®, wire numbers. From the main unit of resistance, extract the negative path then the positive path to the power source. The more complete an extraction, the easier it will be to pinpoint any electrical malfunction. As a reminder, components are drawn in their "de-energized" positions. As you extract, be sure to include those parts of the circuit that need to be energized, i.e., contacts, switches, etc. Equipment, diagrams, devices, and other items differ from manufacturer; however, these rules can be adapted to most equipment. Below are suggested procedures to complete the extraction: Procedures: 1. Locate main unit of resistance – Cranking Motor (B1). 2. Extract negative paths. a. Cranking Motor (B1) to battery negative. b. Start Relay (K15) to battery negative. c. Crank Relay (K2) to battery negative. 3. Extract positive paths. a. Cranking Motor (B1) to battery positive. b. Start Relay (K15) to battery positive. c. Crank Relay (K2) to battery positive. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-19 SW J3ABR3E032 00AD-VII ELECTRICAL MALFUNCTIONS Typical electrical malfunctions are opens, shorts, grounds, and low power. Each malfunction will be discussed including their causes, symptoms, and procedures for locating them. Opens An open is an incomplete path for current flow within the circuit (Figure 2-17). The example shows the positive wire not connected to the lamp. If there is an open, there is no current flow, and the component will not operate. Cause - Opens can occur when a conductor breaks, a fuse blows, a relay or switch contact fails to close properly or when Figure 2-17: Open Circuit any device within the circuit fails to provide a complete path for current to flow. Symptoms - The symptoms of an open include the circuit inoperative and the protective device not actuated. Procedures - The possible location of an open can be anywhere in the circuit. The open can be located on the positive or negative side of the unit of resistance. The open can be found using a voltmeter or ohmmeter. Figure 2-18 shows a voltmeter being used to locate an open. In the example, the open can be found in the positive wire between the control device (switch) and the resistive device (lamp). Using the voltmeter requires the circuit to be energized. The meter is used to measure voltage at various points to locate the OPEN. Connect the meter into the circuit by placing the black test lead on the negative Figure 2-18: Locating Open Circuit via Voltmeter CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-20 SW J3ABR3E032 00AD-VII side of the circuit and the red test lead on the positive conductor at the main unit of resistance. Observe the meter indication. If the meter indicates applied voltage (24 VDC) a difference of potential exists, and the circuit back to the power source will be good. However, if the meter indicates 0 VDC, there will be no difference of potential and the open will be located between the power source and the test point. Check the remaining positive terminals in sequence by moving the red test lead back toward the power source. When the meter changes from zero to applied voltage (24 V), the OPEN has been located. The OPEN fault will be between the last zero reading and the first voltage reading. Figure 2-19 shows an ohmmeter being used to find opens. On digital multimeters (DMM), the diode function or audible continuity test (beep) may be utilized to check for open circuits. This may be misleading because if the DMM was placed across a resistance a short beep will also sound. Continuity will be found when the DMM has been placed across a low resistance such as an intact wire. With the ohmmeter, the technician must observe two very important precautions. First, power to the circuit must be tested as "DE-ENERGIZED.” This must be done to prevent damage to the meter and personnel. Most ohmmeters supply their own power. Any voltage or current that may be encountered by the meter, could cause damage to its internal components. Second, the circuit components and conductors must be isolated to prevent erroneous Figure 2-19: Locating Open Circuit via Ohmmeter readings. If not, any amount of resistance will be detected by the ohmmeter. Remember the characteristics of a parallel circuit. The inaccurate resistance reading could "fool" the technician into thinking the problem has been located. The ohmmeter indicates continuity as low resistance. A DMM would read “OL” or infinity (∞) when the circuit is open. The term continuity means a zero resistance present as compared to an unbroken wire or a resistance value of a device within a circuit. When using an ohmmeter, locate an open by placing the black lead on one end of a circuit segment and the red lead to the other end of the circuit segment. An infinity reading (OL) indicates an OPEN exists between the two test probes. A ZERO, or small resistance reading, indicates continuity of the circuit segment. Test each circuit segment or conductor until the open has been located by an infinity reading on the meter. If using the audible continuity test function, continuity will be indicated by an audible beep from the meter. In figure 2-11, an ohmmeter was used to check segments of the circuit. The open can be located between the switch and the lamp. When checking the segment between the fuse and the lamp, the meter will indicate infinite ohms, meaning an open conductor between the test CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-21 SW J3ABR3E032 00AD-VII leads. However, when the red lead has been moved back toward the power source, the meter indicates low resistance (0.0 Ω) indicating continuity for that segment. If the technician uses a DMM with the audible continuity function, the same precautions must be observed as with the conventional ohmmeter. De-energize the circuit and isolate the components and conductors. Place the meter leads across segments of the circuit. If the technician hears the meter "beep", the connection or component will be good. If the meter does not emit a "beep" the connection or component will be open. Remember, while using an ohmmeter, the power must always be "OFF." Direct Short A direct short is a condition where the unit of resistance is bypassed and causes the current to increase to a point where the protective device actuates. Figure 2-20 illustrates the bypass by creating a shortcut back to the power source. Cause - Positive and negative conductors make direct contact and result in a direct short. Symptoms - The symptoms of a direct short include the circuit being inoperative and the protective device actuated. Also, if the excessive current remains in the circuit long enough, the insulation on the wires may begin to melt or burn. Figure 2-20: Direct Short Procedures - The location of a direct short will always be between a positive and negative conductor. Since the fault does not occur until the control device has been turned on, the fault will be located after the control device (between the control device and unit of resistance). Direct shorts are located using an ohmmeter (Figure 2-21) mainly due to the actuated protective device removing the power in the circuit during a short or overcurrent condition. An ohmmeter will be the only method of locating the direct short. When symptoms indicate that a direct short exists, the power to the circuit Figure 2-21: Locating Direct Short via Ohmmeter CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-22 SW J3ABR3E032 00AD-VII must remain "OFF" and the positive conductors in the circuit must be isolated. Using the ohmmeter, place one lead of the meter on the negative conductor and check each positive conductor with the other test lead. An infinity or “OL” reading on the ohmmeter, or no "beep" from the DMM, indicates no short is present. A low resistance reading on the ohmmeter, or an audible "beep" from the DMM, indicates continuity between the two test points and the location of the direct short. The direct short will be between the positive wire to the right of the switch, and the negative wire indicated by a low resistance reading. Cross Short A cross short will be one of the most difficult faults to troubleshoot as it involves two or more circuits. Figure 2-22 illustrates a cross short and shows two circuits operating from one control device (switch). With either switch is turned on, both circuits operate. Cause - A cross short occurs when the positive conductors of two (or more) Figure 2-22: Cross Short independent circuits make contact. This cross connection, or cross short, causes the units of resistance in both circuits to operate when only one control device has been placed to the "ON" position. Symptoms - Two or more independent circuits operate from one control device and the protective device may or may not actuate. The activation of the protective device depends on the current rating of each circuit and the size of the protective devices involved. The positive conductors in both paths, contacting each other. As a result, both lamps operate at the same time by closing either control switch. Procedures - Cross short conditions will not be as common as direct shorts. They are more complex to troubleshoot because they affect more than one circuit. The cross short shown in figure 2- 15 is caused by two positive wires connecting to each other. As a result, both lamps operate at the same time by closing either control switch. Figure 2-23 shows the top switch controlling both circuits. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-23 SW J3ABR3E032 00AD-VII The location Figure 2-23: Locating Cross Short via Ohmmeter of a cross short will be between the control devices and units of resistance of two or more independent circuits. An ohmmeter will be used for locating electrical short malfunctions, so the power to the circuits must be “OFF.” The technician must isolate all the positive conductors of the circuits involved. Place one lead of the ohmmeter on a positive conductor of one circuit. Place the other ohmmeter lead on the positive conductors of the other circuit, one at a time. If the cross short was not found, move one ohmmeter test lead to the next positive conductor in the first circuit. Then, move the other test lead through the second circuit as before (one at a time). Repeat these procedures until the location of the cross short can be isolated. A zero reading on the ohmmeter, or a “beep” from the DMM, indicates the location of the cross short. The cross short will be located between the wires to the right of each switch. Shorted Control The shorted control (Figure 2-24) condition energizes control devices when the circuit is intended to be de-energized. These are often easily identified as they affect switches, relays and solenoids. Cause - A shorted control is caused by the contacts of a control switch, or a relay being stuck or welded closed. Shorted controls are usually the result of over current conditions or the constant opening and closing of the Figure 2-24: Shorted Control electrical contacts. Symptoms - The symptoms of a shorted control include the circuit continues to operate with the control device in the “OFF” position and the protective device be actuated. Procedures - When checking for a shorted control condition, the circuit power must be off, and the control device must be isolated as illustrated in figure 2-20. Using an ohmmeter, place the leads across the contacts of the control device or switch with the control device or switch in the "OFF" position. An “OL” infinity reading on the ohmmeter, or no audible "beep" from the DMM, indicates CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-24 SW J3ABR3E032 00AD-VII proper switch or control devices operation. A zero reading on the ohmmeter, or a "beep" from the DMM, indicates a shorted control device or switch as illustrated in figure 2-25. Figure 2-25: Locating Shorted Control via Ohmmeter Grounds If a positive conductor contacts conduit, frame, chassis or any other metallic part of a wiring system, the circuit grounds out. Figure 2-26 illustrates a grounded circuit condition. This will be like a direct short; however, the circuit is being grounded complete while bypassing the unit of resistance. Cause - Wires moving by vibration can cause grounds. The vibration forces wires to rub along a surface while slowly Figure 2-26: Grounded Circuit removing the protective insulation from the wire. When enough insulation is removed, the metal conductor contacts the metal of the frame or a metal conduit creating a path from positive to ground. Symptoms - A ground will have the same symptoms as a direct short. The symptoms of a grounded circuit include the circuit inoperative, and the protective device actuated. Power bypasses the unit of resistance and goes to ground. This causes current to increase and the protective device to actuate. Procedures - The location of a ground electrical malfunction can be found between a positive conductor and the frame or ground using an ohmmeter. The procedures for locating a ground will be like the procedures for locating direct shorts with one exception; the frame of the unit will be substituted for the negative conductor. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-25 SW J3ABR3E032 00AD-VII Power must be off to the circuit and each positive conductor, and the main unit of resistance must be isolated. Place the black test lead on the frame ground and the red test lead on the positive side of the unit of resistance. Check for continuity between the test points. Continue checking the positive conductors until continuity is indicated on the ohmmeter (Figure 2-27). Figure 2-27: Locating a Grounded Circuit via Ohmmeter Low Power The low power fault will be a result of reduced voltage/current or increased resistance. Figure 2-28 illustrates a low power condition. Cause - Weak batteries commonly cause low power. It can also be caused by a loose connection, dirty switch contacts or conductors sized too small to carry the load. Symptoms - Electric motors running sluggish, lights burning dim, and relay contacts chattering will be symptoms of a low power Figure 2-28: Low Power malfunction. Procedures - A low power electrical condition can be anywhere within the circuit. To find the malfunction, power to the circuit must remain “ON.” Using a voltmeter, first check the applied voltage across the battery terminals to determine if a weak battery could be the cause of low power. Then, use the DMM to measure voltage across the unit of resistance in the circuit. A voltage drop should indicate the applied voltage. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-26 SW J3ABR3E032 00AD-VII If a low power condition has been determined, the non- resistive components of the circuit must be checked. Recall that wires, fuses, connections, etc., should not offer any resistance and have no voltage drop. Check each wire segment, switch, connection, etc., until an additional voltage drop has been found as illustrated in figure 2-29. This indicates the cause or location of the low power malfunction. For example, if a voltmeter was connected across the terminals of a “closed” switch, no voltage should be indicated on the voltmeter. If voltage indicates, the switch may have dirty contacts causing resistance inside the switch. Any Figure 2-29: Locating Low Power via Voltmeter form of resistance will have a voltage drop across the device. SAFETY PRECAUTIONS Employing safe practices must be the priority when accomplishing any task. Failure to do so could result in damage to the equipment or, even worse, personal injury or death. Understand that you are a valuable resource to the Air Force, and no one wants to see you injured or possibly killed. Everything in this lesson was designed with safety in mind. Do not to operate or troubleshoot any trainer or equipment except under the strict direction of an instructor. General Hazards Remove all jewelry and have the necessary personal protection equipment when troubleshooting generator systems. Generator components may be hot and present a noise hazard when operating. Only work on energized circuits when necessary and stand on rubber mats to reduce the possibility of electrical shock. Generators will have moving parts while it is in operation. Gloves, rags, and loose clothing will not be worn or used around moving machinery. Any adjustment, cleaning, lubrication, or repair will be done with the machinery turned off. If shutdown is not possible, use extreme care in and around the equipment. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-27 SW J3ABR3E032 00AD-VII Work Area Safety Work areas may contain hazards to be aware of so, take the necessary actions to reduce or eliminate the risks. The most common safety issues that can be prevented will include general housekeeping, proper ventilation, lighting, and horseplay. Poor housekeeping can result in any number of accidents. Keep all floors and walkways clean, dry, and free of oil, fuel, or grease. Clean up spilled fluids immediately. Provide suitable waste containers for all waste items such as trash, oily rags, used oils, and fluids. Each container must be properly marked for the type of waste it will hold. Do not leave tools on the floor or around the equipment. If the tools are not in use, return them to their assigned toolbox or bag. Fuel vapors and exhaust fumes pose a serious health hazard. Ensure the work area has proper ventilation to deter collection of these hazards, especially in confined spaces. Keep the work area well-lit to prevent the technician from stumbling in dark areas. Proper lighting also aids in seeing the equipment being worked on without having to reach in blind areas. Horseplay contributes to many accidents around the workplace. Pushing, tripping, electrically shocking and other tricks are a few examples of this seemingly innocent activity. These situations can result in a technician connects with rotating machinery, high and low voltage electricity and injury from falling. Post all warning signs and danger tags to prevent accidents. Standard signs must be used to warn of certain hazards. Noise Hazard - Since the equipment will require operation during the several phases of troubleshooting, technicians will be exposed to hazardous noise during operation. Proper wear of hearing protection will prevent hearing loss. Chemical Hazards - Coolant, fuel, oil, grease, and cleaning solvents all present a chemical hazard for skin contamination. Prolonged exposure can result in serious illness. Wear protective clothing when handling these chemicals. If any hazardous chemicals contact the skin or eyes, rinse the area thoroughly with water and seek medical attention immediately! Electrical Hazards - Many electrical hazards are associated with troubleshooting. The wiring and electrical components present a hazard if conditions begin to deteriorate. Wet conditions and damaged wiring or components present an electrical shock risk. Remain vigilant, know applicable safety rules, regulations, and comply with established safe practices. These practices will go a long way towards keeping technicians free from injury. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-28 SW J3ABR3E032 00AD-VII Complete Workbook Exercise 2b. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 2b: Troubleshoot a DC Electrical System. REFERENCE: SW J3ABR3E032 00AD-VII, Lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your responses to the questions/statements that follow. 1. What are the three most common types of diagrams used in troubleshooting? 2. Which type of diagram gives you an instant overview of a generating system? 3. Besides the schematic diagram, which other type of diagram is useful for extracting circuits? 4. What is the first rule in tracing a circuit? 5. What is making a simple drawing of a circuit known as? 6. What is to be used as a guide to extract a circuit from a connection diagram? 7. What is an OPEN and what meter(s) is/are used to troubleshoot an OPEN? 8. What type of meter(s) is/are used to troubleshoot a direct short? 9. Prior to testing for a direct short, what precaution must be observed to prevent damage to the meter? 10. What two malfunctions have the same symptoms AND similar procedures for troubleshooting? CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-29 SW J3ABR3E032 00AD-VII ADJUST AND TROUBLESHOOT ELECTRONIC GOVERNING SYSTEM OBJECTIVE: 2c. Given TO 35C2-3-444-12 and working as a team, adjust the set points and troubleshoot an electronic governing system with no more than two instructor assists. The governor system controls engine speed, which affects the efficiency of the power we produce. Electronic governors provide a solid-state control system to maintain precise engine speed (frequency) and responds quickly to load changes. SAFETY PRECAUTIONS Ensure engine has been shut down prior to performing maintenance. Remove all jewelry. Engine may be hot, use caution around components. Avoid sparks, open flames, or other sources of ignition around fuel system components. Do not operate generator without wearing appropriate PPE. Ensure adequate ventilation for exhaust fumes. ADJUST AND TROUBLESHOOT AN ELECTRONIC GOVERNING SYSTEM From time to time, the engine governing system may need adjusting or troubleshooting. Every manufacturer will have different versions of their governors, but all operate off the same principle: 1. Use a governor control unit (GCU). 2. Receive a signal from a magnetic pick-up (MPU). 3. Move the fuel actuator to control the fuel. Consult the proper T.O. when adjusting, testing, and/or troubleshooting an electronic governing system. Governor Control Unit Testing The following procedures are for a MEP-806A: 1. Operate generator and verify governor operating inefficiently/incorrectly - can indicate a malfunction with the governor or associated parts. a. Engine hunting/surging (not maintaining steady speed). b. Unable to adjust frequency or not able to maintain 60 Hz while under load. 2. Shut down generator and open the control panel door to expose the GCU. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-30 SW J3ABR3E032 00AD-VII 3. Set digital multimeter to VDC. Hold the MASTER SWITCH in the “START” position. a. Check for voltage on pin positions 1, 3, 5 on the GCU to ground. The meter should read battery voltage. b. If no voltage is read between any of the connections, the GCU is not receiving the proper voltage and the wiring harness should be checked. NOTE: With the generator running, the voltage will read zero. 4. Place MASTER SWITCH in OFF position. a. Connect multimeter leads to terminals 19 and 20 on the GCU and move the MASTER SWITCH to the START position. b. Reading should be battery voltage when the generator does not crank. c. If there is no voltage between terminal positions, the GCU is not functioning properly and should be replaced. NOTE: With the generator running, there will be battery voltage. 5. Place the MASTER SWITCH in OFF position. a. Connect multimeter leads to terminals 19 and 18 on the GCU. b. Move the MASTER SWITCH to the START position. c. Reading should be zero voltage when the generator does not crank. d. If there is voltage between the terminal positions, the GCU is not functioning properly and should be replaced. Shutdown - Follow all procedures listed in the T.O. and perform a post-operational inspection. MAGNETIC PICKUP (MPU) SENSOR TROUBLESHOOTING During testing of the governor, the T.O. may lead to testing an MPU. The following steps will provide an overview of the process. Remove faulty MPU sensor. 1. Wiring a. Tag and label wiring. b. Disconnect wiring. 2. Inspect MPU sensor connections and wiring for: a. Cracked wire casing. b. Stripped or damaged threads. c. Corrosion. d. Other visible damage. 3. To remove MPU, follow these steps: a. Using proper tool and loosen the MPU jam nut. b. Remove the MPU CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-31 SW J3ABR3E032 00AD-VII Inspect New MPU 1. Inspect for signs of damage or deterioration. 2. Verify part number/cross referenced number. Install New MPU 1. Screw MPU into flywheel housing until contact is made with top surface of gear tooth on flywheel. 3. Back MPU out one complete revolution and tighten jam nut. 4. Connect electrical leads and remove any placed tags. 4. Connect negative battery cable. 5. Adjust MPU IAW T.O. Check and Adjust MPU 1. Release control panel by turning two fasteners and open control panel slowly. 2. Isolate wire 147C from terminal 16 and wire 148C from terminal 17 of GCU. 3. Set digital multimeter for ohms and connect to ends of disconnected wires 147C and 148C. Digital multimeter should indicate between 800 and 1100 ohms. 4. Leave multimeter connected to wires 147C and 148C and set multimeter for AC volts. 5. Crank engine with DEAD CRANK switch and observe multimeter. Multimeter indication should be between 2.0 and 3.0 VAC. 6. To adjust output voltage, loosen jam nut and turn MPU in no more than one-eighth turn at a time to increase output voltage, and out no more than one-eighth at a time to decrease output voltage. Tighten jam nut. 7. Repeats previous two steps until proper output voltage is achieved. 8. Remove multimeter, connect wires to governor control unit. 9. Close and secure control panel. 10. When all testing and adjustments have been made reconnect the negative battery terminal and run the generator for serviceability. Shutdown - Follow all procedures listed in the T.O. and perform a post-operational inspection. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 2-32 SW J3ABR3E032 00AD-VII Complete Workbook Exercise 2c. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 2c: Adjust and Troubleshoot Electronic Governing System. REFERENCE: SW J3ABR3E032 00AD-VII, Lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your responses to the questions/statements that follow. 1. What is another term used for erratic engine speed? 2. What must be done before adjusting, testing and/or troubleshooting an electronic governing system? 3. What voltage will be displayed on the digital multimeter when checking pins 1, 3, and 5 of the GCU to ground when the MASTER SWITCH in the “START” position? 4. Name three items the MPU connections and wiring are inspected for. 5. What must be accomplished with the new MPU before installation? 6. During installation, how far is the MPU screwed into the flywheel housing? 7. To adjust the MPU to increase or decrease voltage, the MPU will be rotated how much each time until the desired voltage is obtained? 8. What is the last step to be accomplished after replacing the MPU? CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 3-1 SW J3ABR3E032 00AD-VII UNIT 3. BATTERY CHARGERS OBJECTIVE: a. Given a manufacturer's manual and working as a team, inspect, adjust and troubleshoot a battery charger with no more than two instructor assists per task. INFORMATION Engine starting systems require battery power to turn over the engine. To ensure the system has enough cranking amperage and voltage, external battery charges are used to maintain the battery in the proper condition. When the battery chargers fail, technicians will need to troubleshoot, repair, or replace them. OBJECTIVE: 3a. Given a manufacturer's manual and working as a team, inspect, adjust and troubleshoot a battery charger with no more than two instructor assists per task. SAFETY PRECAUTIONS Before beginning any sort of troubleshooting assessment, ensure the battery charger has been disconnected from both the input power source (AC manufacturer’s power) and the battery. Remove all jewelry before entering the work area. WARNING: Batteries contain corrosive acids and create explosive gases during charging and discharging. INSPECTION PROCEDURES Installations use many types of battery chargers. Before beginning any inspection or troubleshooting, reference the manual to ensure all steps can be accomplished IAW manufacturer’s recommendations. If any discrepancies are found during the inspection, do not operate the battery charger until the discrepancies have been fixed. Begin by checking for frayed, cut, or damaged power cords. Look for broken or burnt connectors. Inspect for dust or accumulate dirt. Verify the general condition of the charger. ADJUSTMENT PROCEDURES For chargers that remain hooked up to a standby generator (permanent), a minimum voltage will normally be maintained with only a selection for desired charge minimum voltage (12 or 24 VDC). The provided setup and operations manual will give more details on these types of charges. For external chargers used to charge a dead battery, some set up and adjustments may need to be accomplished. Ensure to consult the operator’s manual for the proper technique to be used. As an example, the Optima Digital 1200 is used to show the procedures involved in the adjustment process. The Optima Digital 1200 charger can be transported to a site or kept in room or bay for use at the shop. The application on the charger use is dependent on the battery condition and type of battery being used. Fortunately, technology has afforded the technician to utilize their time CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 3-2 SW J3ABR3E032 00AD-VII elsewhere as the charger can enhance the performance of the battery and extend battery life without constant monitoring. The Optima Digital 1200 is specifically designed for use with all Optima 12V batteries to include other high performance 12V AGM, 12V standard flooded lead-acid and standard 12V AGM batteries. It provides a quick and easy charging option by simply choosing the battery type. For example: 1. Profile 1 – Engine Starting – High performance AGM: Redtop and Bluetop. 2. Profile 2 – Deep Cycles – High Performance AGM: Yellowtop and Bluetop. 3. Profile 3 – Standard Flooded lead-acid and AGM (large): auto, marine, truck, RV. 4. Profile 4 – Standard Flooded and AGM (small): motorcycle, tractor, power sport. Once the battery type has been determined, apply the following steps: 1. Connect the red POSITIVE cable clamp to the POSITIVE battery post. 2. Connect the black NEGATIVE cable clamp to the NEGATIVE battery post. 3. Plug the charger into an outlet. 4. Charger will automatically perform a quick self-test of the display and all LEDs. Following the self-test, a prompt will display, and directional arrows will allow the technician to make a quick set selection. a. Pre-Charge Battery Status – The display will provide the current state of battery in % of charge and the DC volts in the numeric display. 5. Choose BATTERY TYPE that best matches the battery being used. After a few minutes, the charger will begin its multi-stage charging process checks and sequence through the illustrated LCD screens highlighted below: a. Analyzing Battery Mode b. Charging Battery Mode c. Conditioning Battery Mode d. Maintaining Battery e. 30 Day Recondition Mode 6. Battery Auto-Maintainer by Connection Type – Choose a maintainer connection type that matches the setup which is commonly “Charging with DC Clamps out of a vehicle”. NOTE: If at any time a fault is identified by the charger, the following will appear: i. “Check Battery” icon red LED will illuminate. ii. The charger will have an audible “chirp” identifying attention is needed. iii. A fault message will be displayed in the LCD center display. The Optima Digital 1200 is just one of many battery chargers available for maintaining generator batteries and is incredibly simple to use. Always read the manufacturer’s manual before operation allowing the technician to troubleshoot the battery charger in the event of a failure during the charging process. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 3-3 SW J3ABR3E032 00AD-VII TROUBLESHOOT BATTERY CHARGER Troubleshooting methods for battery chargers will vary depending on the type of charger used. Battery chargers permanently connected to standby units that fail to charge a battery, should be tested. Begin by verifying external AC power is present at the battery charger. Test any and all fuses to verify serviceability. Use a multimeter and check for output voltage. Consult the user’s manual for the correct voltage output for the battery being charged. Every external charger will be slightly different to troubleshoot, but the Optima 1200 has five possible trouble conditions. 1. Reverse polarity - check connection red positive cable clamp or ring terminal to positive post. 2. Less than 1.25V available. a. Verify: i. Both leads from the charger have been connected to the battery. ii. Connection type (clamp or ring terminal) was connected correctly. iii. Auxiliary ring terminal connecter remains securely plugged into the charger. iv. Battery voltage - may be too low to accept a charge (replace the battery). 3. Charger Hi-Temp. a. Ambient temperature and/or unit temperature too high to charge at the time of attempted operation. i. The charger will automatically resume charging when appropriate. 4. Unable to Charge (Check Battery). a. Check battery voltage with Pre-Charge Status. i. If greater than 12.0 volts, restart charger. ii. Do not repeat more than once. iii. If charging fails again, replace the battery. b. If less than 12.0 volts, replace the battery. c. Verify battery attempting to charge has been rated as a 12V battery versus a 6V battery or other unsupported voltage. 5. Out of Range (battery greater than 17VDC). a. Battery voltage indicates high. b. Check to see if another battery has been connected- remove additional battery. c. Verify another charger or maintainer source has not been connected or energized. i. Remove if either is present. Ensure the engine has been shut down before checking the battery and/or battery charger system. Not all battery chargers will have these same errors. Refer to the operator’s manual applicable to that battery charger for any corrective actions. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 3-4 SW J3ABR3E032 00AD-VII Complete Workbook Exercise 3a. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 3a: Battery Chargers. REFERENCE: SW J3ABR3E032 00AD-VII, Lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your responses to the questions/statements that follow. 1. How many battery profiles will the Optima Digital 1200 maintain? 2. What three things occur if there is a fault with the Optima Digital 1200 battery charger? 3. What must be accomplished if the battery fails to charge, you have restarted the charger, and the voltage is greater than 12V? 4. What is considered “Out of Range”? CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 4-1 SW J3ABR3E032 00AD-VII UNIT 4. INSPECT, TEST AND REPLACE RECTIFIER ASSEMBLY OBJECTIVE: a. Given procedures and working as a team, inspect, test and replace a rectifier assembly with no more than two instructor assists. INTRODUCTION A generator’s alternator provides the output power to the customer. When an alternator fails to produce an output voltage, the rectifier assembly may need to be inspected, tested, and possibly replaced. Although this may not occur very often, it will be very likely a technician will run into this a least once. The knowledge and familiarization of the process will aid in the expedited inspection, test or possible replacement of rectifier parts and components. OBJECTIVE: 4a. Given procedures and working as a team, inspect, test and replace a rectifier assembly with no more than two instructor assists. INFORMATION For mobile military specification (MIL-SPEC) generators, the MEP-80X series generators have proven to be the work horse for the Air Force. All procedures performed during this objective will be done on its alternator assembly, specifically the Marelli alternator assembly. The procedures are similar on all generators but always consult the manufacturer’s manual or T.O. for exact procedures. SAFETY PRECAUTIONS Before beginning any work, adhere to the following procedures: 1. Ensure the generator is shut down and engine has stopped rotating before beginning maintenance. Failure to do so will result in injury or death. 2. Verify batteries are disconnected. 3. Lockout/tagout generator. 4. Ensure the generator has been disconnected from any other power source, i.e., parallel connection. 5. Remove all fuses. 6. Discharge all capacitors and any residual voltage in the rotor, stator and the exciter. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 4-2 SW J3ABR3E032 00AD-VII INSPECT ROTATING RECTIFIER Perform the following to complete an inspection of the rectifiers - always refer to the proper T.O. or manufacturer’s manual during all procedures: Inspect Diodes 1. Disconnect the negative battery cable from the battery and lockout/tagout the generator. 2. Remove the rear housing panel of the generator. 3. Remove the end bell cover plate(s). NOTE: It will be necessary to bar (turn) engine to position a specific area of the rotating rectifier at one of the end bell access holes. Use center bolt on harmonic balancer to turn engine. 4. Visually inspect rotating rectifier assembly for: a. Broken/cracked diode casing. b. Mounting for security. c. Broken wires. d. Signs of chaffing. e. Burnt or burning components. OPERATIONAL TEST/INSPECTION If failure of a rectifier should be suspected, testing the serviceability of the rectifier component will be required. Follow these general procedures: Removal 1. Disconnect the negative battery cable on the generator. 2. Lockout/tagout generator. 3. Remove the generator rear housing panels, end bell housing, and main bearing. 4. Tag main rotor and diode leads. 5. Remove diode leads from the exciter rotor. 6. Remove nuts, lock washers, washers and main rotor leads from terminal bolts. Discard the lock washers. 7. Mark the position of the rotating rectifier assembly for ease of reassembling. 8. Remove the rotating rectifier assembly by using two screwdrivers to pry the assembly from the rotor shaft. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 4-3 SW J3ABR3E032 00AD-VII Testing 1. Remove the rotating rectifier assembly if not already accomplished. 2. Remove nuts, washers, surge suppressor, and diode mounting plates from the terminal bolts. 3. Set digital multimeter for ohms and connect positive lead to one side and negative lead to other side of each diode while recording the reading from each diode. 4. Reverse ohmmeter leads across the diode - record meter reading. 5. Resistance (ohms) should show continuity in one direction and no continuity in reversed direction. 6. If readings show continuity or no continuity in both directions, the diode is defective and must be replaced. Replacement 1. Remove the rotating rectifier assembly, nuts washers, surge suppressor and diode mounting plates from the terminal bolts. 2. Remove nut, lock washer, and diode from the rotating rectifier plate and discard the lock washer. 3. Install the diode on the rotating rectifier plate and nut; torque to 28-30 in-lbs. 4. Install diode mounting plates and surge suppressor on terminal bolts with washers. 5. Install rotating rectifier assembly. Installation 1. Install the rotating rectifier assembly in the same position as previously marked upon removal, using a tube to evenly apply pressure to the plastic support. 2. Install main rotor leads on terminal bolts with washers, new lock washers, and nuts - remove any tags. 3. Install diode leads on the exciter rotor and remove any tags. 4. Install end bell and rear housing panel. 5. Reconnect the negative battery cable. 6. Test the generator. During the performance portion of this objective, some of the components will already be removed to reduce time required for the performance, but the techniques used will remain the same. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 4-4 SW J3ABR3E032 00AD-VII INSPECT SURGE SUPRESSOR-VARISTOR As previously discussed, the surge suppressor for the diodes will often be called a varistor. The varistor absorbs any fluctuations in voltage or current to protect the diodes. Should a diode require replacement, the varistor should be inspected to verify serviceability. Inspect For General Condition Normally, the varistor will be inspected at the same time as the rectifier assembly. Check connections for security and general appearance. Look for discoloration and replace if a burned appearance is identified. Testing To test the varistors, begin by: 1. Shutdown the generator set. 2. Disconnect the negative battery terminal and lockout/tagout the unit. 3. Remove the load output terminal board from the generator set IAW T.O. 4. Tag and disconnect all varistor leads. 5. Remove the nuts, bolts and varistors from the load terminal board assembly. 6. Inspect the varistor for obvious signs of external damage including burnt areas or scoring. 7. Set digital multimeter for ohms and test by connecting digital multimeter leads to the varistor’s terminals and note multimeter reading. 8. Reverse digital multimeter leads and note digital multimeter readings. 9. Multimeter indications should be “OL” ohms in both directions. 10. If other than "OL" is read in both directions, the varistor is defective and must be replaced. Installation Reinstall the varistor on the load output terminal board assembly with bolts and nuts. Connect the varistor leads and remove any tags. Reinstall the load output terminal board assembly IAW T.O. Finally, perform an operational check of the generator. CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR 4-5 SW J3ABR3E032 00AD-VII Complete Workbook Exercise 4a. Place your answers on a separate sheet of paper. If you have any questions, discuss them with your instructor. WORKBOOK EXERCISE 4a: Inspect, Test and Replace a Rectifier Assembly. REFERENCE: SW J3ABR3E032 00AD-VII, Lecture notes. INSTRUCTIONS: Do not write in this book. Use a separate sheet of paper to document your responses to the questions/statements that follow. 1. What is the rotating rectifier assembly visually inspected for? 2. A diode is considered defective and needs replacing if this value is displayed on the digital multimeter display. 3. What value will be displayed on the digital multimeter for a functioning varistor? 4. What is the last step to be accomplished after reinstalling the rotating rectifier assembly? CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR  CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR BIBLIOGRAPHY February 2012. OPTIMA CHARGERS, Digital 1200 12V Performance Charger and Battery Maintainer User Guide. Milwaukee: OPTIMA. 1 September 1993. Technical Order 35C2-3-444-12, Unit, Direct Support, and General Support Maintenance Manual. Departments of the Army and the Air Force, and Headquarters , U.S. Marine Corps. A CUI//REL TO: US, EG, GR, JO, KE, KU, LG, PH, SR