Onan Marine MDL3 MDL4 MDL6 Service Manual 934-0500

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MDL3 MDL4 MDL6 .s 1 , ~- I 934-0500 . 8-91 Printed in U.S.A.

Safety Precautions Before operating the generator set, read the Operator’s Manualandbecomefamiliarwith it andvourunit. Safeandeffl- exhauster. dent operatlon can be achleved onli if the unit is properly operated and maintained. Manyaccidents are caused byfail- ure to follow fundamental rules and precautions. Throughout this manualyou will notice symbolswhich alert you to potentiallydangerousconditionsto the operator, service personnel, or the equipment itself. . D’ This symbol warns of immedlate hazards which will result in severe personal Injury or death. 1 - 1 Thissymbol refers to a hazard or unsafe practlce which can result in severe personal injury or death. [A CAUTiON 1 Thls symbol mfers to a hazard or unsafe practlce which can result in personal Injury or product or properfy damage. FUEL, ENGINE OIL, AND FUMES ARE FLAMMABLE AND TOXIC. Fire, explosion, and personalinjurycan result from improper practices. Benzene and lead, found in some gasoline, have been identifiedby some state and federal agencies as causing cancer or reproductive toxicity. When checking, draining or adding gasoline, take care not to ingest, breathe the fumes, or contact gasoline. Used engine oils have been identified by some state or federal agencies as causingcancer or reproductive toxicity. Whencheckingor changingengineoil, take care notto ingest, breathe the fumes, or contact used oil. Do not fill fueltankswith the engine running. Do notsmoke around the generator set area. Wipe up any oil or gas spills. Do not leaveoily rags in engine compartment or on the generator set. Keep this and surrounding area clean. lnspectfuel system beforeeachoperationand periodically while running. Equip the engine fuel supply with a positive fuel shutoff. Always disconnectthe battery ground (-) leadfirst and re- connect it last. Make sure you connect the battery cor- rectly. A direct short across the battery terminals can cause an explosion. Do not smoke while servicing batteries. Hydrogen gas given off during charging is very explo- sive. 0 Be sure propulsionand generator set engine exhaust systems are free of leaks. Performthorough, periodic inspec- tions of the exhaust system and repair leaks immediately. Exhaust gases are deadly. 0 Never sleep in the vessel with the generator set running unless the vessel is equipped with an operating carbon monoxide detector. . 3 HOT COOLANT CAN CAUSE SEVERE PERSONAL INJURY 0 Hot coolant is under pressure. Do not loosen the coolant pressure cap while the engine is hot. Let the engine cool before opening the pressure cap. MOVING PARTS CAN CAUSE SEVERE PERSONAL INJURY OR DEATH Do not removeany belt guards or covers with the generator set running. Keep hands and loose clothing away from moving parts. Do notwearjewelry while servicingany part of the generator set. Never step on the generator set (as when entering or leav- ingthe engine compartment). It can stress and break unit components, possible resulting in dangerous operating conditions. . . from leaking fuel, leaking exhaust fumes, etc. Beforeperformingany maintenance on the generator set, disconnect its batteries to prevent accidental starting. do not disconnect or connect battery cables if fuel vapors are present. Ventilate the generatorset compartment or bilge thoroughly with the power exhauster. ELECTRICAL SHOCK WILL CAUSE SEVERE PERSONAL INJURY OR DEATH Do not make adjustmentsinthe control panel or on engine with unit running. High voltages are present. Work that must be done while unit is runningshould be done only by qualified service personnelstandingon dry surfacesto reduce shock hazard. . U 0 DO NOT CONNECT THE GENERATOR SET TO THE PUBLIC UTILITY OR TO ANY OTHER ELECTRICAL P POWER SYSTEM. Electrocution or damage to property can occur at a site remote from the boat where line or equipment repairs are being made if the set is connected to the power system. An approvedtransfer switch must be used if more than one power source is to be made available to service the boat. Keep a fire extinguisher available in or near the engine compartment and in other areas throughout the vessel. Use the correct extinguisher for the area. For most types of fires, an extinguisher rated ABC by the NFPA is available and suitable for use on all types of fires except alcohol. 0 Do notworkon this equipment when mentallyor physically fatigued, or after consuming any alcohol or drug that makes the operation of equipmentunsafe. M8 EXHAUST GASES ARE DEADLY Provideadequate ventilation. Equip the bilgewith a power Copy and post these suggestions In potential hazard areas of the vessel.

Table of Contents SECTION TITLE PAGE SAFETY PRECAUTIONS ......................................................... ii 1 INTRODUCTION ............................................................. 1-1 About this Manual .......................................................... 1-1 Test Equipment ............................................................. 1-1 Safety Considerations ....................................................... 1-1 Generator Set Removal ..................................................... 1-2 GENERATOR AND VOLTAGE REGULATOR ..................................... 2-1 Generator Description ...................................................... 2-1 Generator Operation ........................................................ 2-2 Voltage Regulator ........................................................... 2-3 Generator Service .......................................................... 2-5 3 GENERATOWREGULATOR TROUBLESHOOTING .............................. 3-1 Preparation ................................................................ 3-1 Troubleshooting Procedures ................................................ 3-1 4 GENERATOWREGULATOR TESTS .............................................. 4-1 General ................................................................... 4-1 (A) Testing AC Residual Voltage ............................................. 4-1 (B) Testing Commutating Reactor ............................................. 4-1 (C) Testing Rectifier Bridge CR21 and Suppressor RV21 ........................ 4-1 (D) Flashing the Field ....................................................... 4-2 (E) Testing Reference Transformer ........................................... 4-2 (F) VR21 Replacement ....................................................... 4-2 (G) Testing Rotating Rectifiers ............................................... 4-3 (H) Testing Exciter Stator .................................................... 4-3 (J) Testing Exciter Rotor ..................................................... 4-4 (K) Testing Generator Stator ................................................. 4-4 (L) Testing Generator Rotor .................................................. 4-5 (M) Wiring Harness Check ................................................... 4-6 (N) Testing Regulating Transformer T21 ....................................... 4-6 . (P) Voltage Adjustment ...................................................... 4-7 (Q) Reconnection ........................................................... 4-7 General ................................................................... 5-1 MDL Control ............................................................... 5-1 ENGINE CONTROL ADJUSTMENTS/TESTS .................................... 6-1 General ................................................................... 6-1 (A) Battery Checkout ......................................................... 6-1 (B) Battery Cable Checkout .................................................. 6-1 (C) Battery Charging Checkout ............................................... 6-1 (D) Solenoid Checkout ...................................................... 6-1 (E) Relay Checkout ......................................................... 6-2 (F) Fuel Solenoid Checkout .................................................. 6-2 (G) Switch Checkout ........................................................ 6-2 (H) Solenoid Checkout ...................................................... 7-1 7 WIRING DIAGRAMS .......................................................... 7-1 2 5 ENGINE CONTROL ................................. ......................... 5-1 . 6 . iii

Section 1 Introduction ABOUT THIS MANUAL This manual covers troubleshooting and repair information for the generator and control. Refer to a separate engine service manual 934-0750 when servicing the engine. This manual has separate sections for the generator and voltage regulator, engine control, and associated wiring diagrams. While the wiring diagrams at the end of the manual are included to help trace or isolate prob- lems, it is suggested that service personnel use the wiring diagrams shipped with the unit for troubleshooting. Repair information for solid state printed circuit boards is not extensive because they lend themselves more to replacement than repair. Application of meters or hot soldering irons to printed circuit boards by other than qualified personnel can cause unnecessary and expen- sive damage. Repair of the printed circuit boards is not recommended except by the factory. A return and exchange service has been initiated whereby faulty printed circuit boards can be returned to the Distributor and exchanged for good units. For more information, contact your Onan Distributor. b High voltage (Megger) testing or high 1 - 1 potential (high pot) testing oigenera- tor windings can cause damage to solid state components. Isolate these components before testing. TEST EQUIPMENT Most of the test procedures in this manual can be performed'with an AC-DC multimeter such as a Simpson Model 260 VOM or a digital VOM. Some other instru- ments to have available are: 0 Megger or Insulation Resistance Meter 0 Onan Multitester 0 Wheatstone Bridge 0 Jumper Leads 0 Load Test Panel 0 Variac 0 AC Voltmeter DC Voltmeter Frequency Meter Tachometer or Strobotach See Tool Catalog 900-001 9. Several troubleshooting guides are included in this manual to help the serviceperson locate the cause of various malfunctions. Note that some malfunctions might have several possible'causes. For this reason,the service person may haveto investigate several problem areas in order to isolate the source of the malfunction. Because of the complexity of the product, a troubleshooting chart cannot list every malfunction and cause. In some situations, the serviceperson will haveto rely on experience and a knowledge of the product to locate the problem and service as required. SAFETY CONSIDERATIONS Always consider the safety aspects of any service procedure. Generator sets present several hazards that the serviceperson must be aware of to safely complete the job. Read through the safety precautions listed on the inside cover and familiarize yourself with the various hazards shown in Table 1-1. Once the hazards are known, approach the job with a safety conscious atti- tude. Being safety conscious is the most effective way to avoid injury to yourself or others. Reduce the chance that an accident will occur by adopting the following safeguards. Safeguards to Avoid Hazards 0 Use Personal Protection - Protect your body by wearing appropriate safety equipment. Protective clothing includes safety shoes, gloves, safety glasses, and hard hats. Leave rings and jewelry off and do not wear loose clothing that might get caught on equipment. 0 Work to Reduce the Hazard - The, workshop area and all pieces of equipment used can contribute to reducing the hazard potential. Keep guards and shields in place on machinery and maintain equipment in good working condition. Store flammable liquids in approved containers, or other ignition source. Keep the workshop clean and well-lighted, and provide adequate ventilation. Keep fire extin- guishers and safety equipment nearby and be prepared to respond to an emergency. 1-1

TABLE 1-1 HAZARDS AND THEIR SOURCE 0 Fire and Explosions -Leaking or spilled fuel -Hydrogen gas from battery -Oily rags improperly stored -Flammable liquids improperly stored 0 Burns -Hot exhaust pipes -Hot engine and generator surfaces -Electrical short in DC wiring system -Carbon monoxide from faulty exhaust pipes, joints, or hangers -Operating generator set where exhaust gases can accumulate 0 Poisonous Gases 0 Electrical Shock (AC) -Improper generator set load connections -Faulty vessel wiring -Faulty electrical appliance -Faulty generator set wiring -Working in damp conditions -Jewelry touching electrical components 0 Rotating Machinery -Jewelry or loose clothing catching in moving parts 0 Slippery Surfaces -Leaking or spilled oil 0 Heavy Objects -Removing generator set from vessel -Removing heavy components 0 Develop Safe Work Habits - Unsafe actions are GENERATOR SET REMOVAL identified as the cause of most accidents involving the use of tools and machines. Be familiar with the equipment and know how to use it safely. Use the correct tool for the job and check its condition before starting. Observe the warnings and cautions in this manual and take special precautions when working around electrical equipment. Do not work alone if possible and do not take risks. Be prepared if an accident does occur. Numerous agencies such as the Red Cross and your local police and fire departments offer basic courses in first aid, mouth-to-mouth resuscitation, and fire control. Take advantage of these offerings so you are ready to respond when an accident happens. Learn to be safety conscious and make safe practices a part of your work routine. Do not work when tired or after consuming any alcohol or drug that makes the operation of equipment unsafe. Service should be performed at location whenever possible due to the generator set size and weight. Some service procedures may require removal from the vessel. While there are many variations, the generator set is usually located in the bilge, and sometimes with limited service space. Because of the variety of installations, it is not possible to specify exact removal proceduresfor any one set. If a satisfactory method cannot be determined, contact the vessel manufacturer to obtain their recommendations. Generator sets are heavy and can l3!ZEEI result in severe personal injury or death if dropped during removal. Use adequate lifting devices to provide sufficient support. Keep hands, feet and body clear while lifting. IAWARNING I INCORRECTSERVICE OR REPLACEMENTOF PARTSCANRESULTINSEVERE PERSONAL INJURY AND/OR EQUIPMENT DAMAGE. SERVICE PERSONNEL MUST BE QUALIFIED TO PERFORM ELECTRICAL AND/OR MECHANICAL SERVICE. P ..

Section 2. Generator/Voltage Regulator GENERATOR DESCRIPTION The YD generator (Figure 2-1) is a four-pole, revolving field, brushless exciter design with drip-proof construc- tion. Single and three phase generators are available for both 50 and 60 hertz models. d The generator rotor is directly coupled to the engine flywheel with a flexible drive disc (engine speed determines generator output voltage and frequency). A centrifugal blower on the drive disc circulates generator cooling air which is drawn in through the end bell and discharged through an outlet in the blower end. . DRIVE DISC BLOWER A ball bearing in the end bell supports the outer end of the rotor shaft. The end bell is attached with four studs that thread into the generator adapter casting. The brushless exciter stator mounts in the end bell while the exciter rotor and its rotating diode assemblies mount on the generator rotor shaft. Within the end bell, leads F1 (+) and F2(-) from the exciter stator winding are connected to the output terminals of the voltage regulator. In addition to the AC output (load) leads, control wires. exit ffom the generator housing. The number of wires depends upon the model and options (see Figure 2-2). END BELL \ FIGURE 2-1. TYPICAL YD SERIES GENERATOR 2-1

CONTROL LEADS THREE-PHASE ll CODE 3 8 53 SINGLE PHASE GENERATOR OPERATION Operation of the generator involves the stator, voltage regulator, exciter stator and rotor, rotating diode assemblies, and the main rotor. See Figure 2-3. A permanent magnet embedded in one exciter field pole begin the voltage build-up process as the generator set starts. Single-phase AC voltage, taken from one of the stator windings, is fed to the voltage regulator as a reference for maintaining the generator output voltage. DC voltage output from the voltage regulator is fed into the brushless exciter stator. b The exciter rotor produces three-phase AC voltage that is converted to DC by the rotating diode assemblies. The resultant DC voltage excites the main rotor winding to produce the stator output voltage for the AC load. 1 EXCITER STATOR ES1489 * - USED ONLY ON 12- AND 24-VOLT SYSTEMS , FIGURE 2-2. SINGLE AND THREE PHASE GENERATOR SCHEMATLC (COMPOSITE) ROTOR SHAFT BRUSHLESS MAIN EXCITER ROTOR ROTOR - - . @+ - ASSEMBLIES W ?! U I I I' EXCITER ' ' 1 : : I I PERMANENT I MAGNETISM MAGNETISM I I MA$~~c~sRTs BRUSHLESS EXCITER STATOR I STATOR ASSY VOLTAGE I REGULATOR 1 ES1490 FIGURE '2-3. EXCITATION BLOCK DIAGRAM 2-2

VOLTAGE REGULATOR The voltage regulator controls the output of the generator's0 that a constant voltage is maintained under varying load conditions. There are two types of voltage regulators used on these sets-transformer and electronic (solid state). The description and operation of each type is covered separately. Transformer Voltage Regulator The transformer voltage regulator is standard equipment on all single-phase generator sets. It is located inside the generator set control box. A typical trans- shown in Figure 2-4. The transformer provides a feed- back loop from the output of the generator to its exciter. . former and a schematic showing circuit application is The number of primary windings and secondary taps will change for 50 hertz and different model applica- tions. See individual model wiring diagrams at the rear of this manual. The transformer primary is connected in series with the generator output leads making it a current boost winding for the secondary. Separate coils in the primary allow the generator to be reconnectedfor other voltages without causing an output voltage unbalance. The transformer secondary is in the exciter circuit and connected through a diode bridge. The diode bridge converts AC to DC for the exciter. Thus the exciter DC boost current is dependent upon the primary/load current. ROTOR DIODE ASSEMBLIES H1 THROUGH H4 ES1491 LO L1 L2 FIGURE 2-4. TYPICAL TRANSFORMER AND CIRCUIT APPLICATION 2-3

Onan Marine MDL3 MDL4 MDL6 Service Manual 934-0500

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