rv generator troubleshooting guide
Contents
1. ztd _ ION3IOS avis Pr ae Se Oo A A AAA E ada wa vid ota ela dd 13 Twig hd AZ W WB me L wea ia ig id gd sd l wd wid esta vw td trid pd id wd old aALISOdAH3LIVB Ee SER EEE GE GG WERON DE 957 005 2067006 1067 00 OZEY O0O 1616006 9946 00 e9ue 00 9905 006 822 008 6625 006 922 008 1666006 6267006 557 006 ZP S 00 899 006 1896006 57624006 8 TOYINOD WERE AAA ees LICO KRA EEE EEE SYOLVYIN39 ONILOOHSI19NOYL 303 NOLLVINYOWNI 1S31 REGULATOR PIN ASSIGNMENT Onan Part Number s 305 0782 01 I U 305 0852 1 305 0809 01 305 0851 305 0809 05 305 0897 305 0826 305 0911 BSE A OWA AC Sense HI 2 2 2 2 2 2 SenseLO Gnd_ 3 3 3 3 3 3 E AEK TA E TW S SW WY WW WE A Wattage Adjust Retum 5 6 _Capacitor Negative 6 nc 6 6 mc nie Ground 5 Capacitor Positive ne 8 8 m ne Se o O M BWL DE WM WW R WWE W U Vs Ea L U WARSAW I w u pul W W Quad Aux StatorQ1 11 11 1 97 1 414 J 11 L SI TAS T EN NEC UN NONE WUW E WM E w CONTROL BOARD P N SUPE2. jeolueuoay Nid 9 NO Un 01 S La sion 29 19 SIOA 29 19 GND 016 14 SIA Z8 18 29 19 SHOA 29 18 20 42 00 Posey ___ UO Iny pouwepie SI 107 MOT _2680 50 He cal A sha sssi Sid sc sa oe oza 94 v3azMviOL3miL Eid _ gor se ser ser sad 9 W3I3WNOLLIONOO val sld bd wd er er ver ver wad izd SNL BLOWS ced wd zw eer ew ze aq dols3iomay veia eer eer eer eza lavISlOWIU preoquo pieoquo pieoquo ig eur peoquQ pieoquQ red 1901 pieoquo peoquo tid ei peoquo pieoquQ peoquo 9018 901 preoqug pieoquo peoquo erid peoquo peoquo peoquo eta LHW 901 s V m l ee Ge ee TI UU La Me DOOR Bu peay DPIIOA yo 20 29 19 Ld 9 1V8 LL LO 0 6 N 0 1VB b bd 01 2 14 14 011 14 b bd 018 14 a are rid sau oHo 199 IA wre wld td std 8 T Tea 5 971 PP o A A GE ES ee l sd zed rw ze sid ved tia MSdOVIO1 O eza gd kd 6d SW eid wd std Std HSY OW zd 6ta sd zd 6d
3. turn off the generator s AC circuit breaker s reconnect the regulator and apply 12 volts through a diode to pin 9 of the regulator plug see illustration while attempting to start the engine CAUTION DO NOT attempt this without the diode If you do there will be fireworks Remove the 12 volts within 1 2 seconds after the engine starts If the genset now continues to run and produces normal AC voltage the generator is OK and the regulator is defective If the genset does not continue to run but produces about 40 of normal AC voltage again the generator is OK and the regulator is defective If no AC voltage is produced the generator may have a problem that is beyond the scope of this guide Re check all wiring for security and signs of damage It may be necessary to take the unit to a qualified repair shop B Check the oil pressure switch as soon as the engine starts Models showing LOP to GND under CON DITIONS REQUIRED TO KEEP RUNNING need the oil pressure switch to be closed to ground when running If the voltage on the LOL LOP SW pin of the control does not go to near zero the switch is not closing These switches sometimes stick open if the generator has not been used or exercised often enough Multiple start stop cycles and or tapping on the oil pressure switch will sometimes fix it It may be neces sary to temporarily jumper the switch to ground to keep the engine running This can be done at the switch or at the OIL LOL LOP SW pin on
4. Check the generator AC output voltage as soon as the engine starts Models showing 1 2 Volts or L1 AC Volts under CONDITIONS REQUIRED TO KEEP RUNNING need this AC voltage to keep running Read between the points shown on the Troubleshooting Chart If the AC voltage readings are good proceed to B below A2 Field Flash If there is no AC check for 10 12 VDC at the FIELD FLASH pin of the control board during cranking If the field flash voltage is not present the control board is defective If the field flash voltage is present the wiring or regulator may be defective To eliminate the wiring check continuity between the FIELD FLASH pin of the control board and pin 7 of the regulator If the continuity is good either the regulator or the field circuit rotor and brushes may be the problem A3 Field Circuit Check the field circuit by unplugging the regulator and measuring the resistance between pins 9 and 10 of the regulator s mating plug This reading should be 22 to 28 ohms If this reading is too high check the brushes and or clean the slip rings use the Slick Stick or a similar tool If this reading is too low there may be a short in the rotor Also check the resistance from pins 9 and 10 to ground This reading should be very high or infinity If not there is likely a ground in the rotor If these reading are all good the regulator is likely defective A4 External Excitation To confirm that the regulator is defective
5. the control board Models showing LOP Open under CONDITIONS REQUIRED TO KEEP RUNNING have electronic governors and require the low oil pressure switch to be closed at starting but open during running When the switch opens the governor module places a ground on the oil pressure input of the control board P1 5 It is OK to temporarily ground P1 5 on this model to keep the engine running NOTE See chart for oil pressure and oil level switch locations If there is AC voltage present on B1 B2 L1 AC as applicable and the correct oil pressure level signal is present at the OIL LOL LOP SW input of the control board and the engine will not keep running the control board is defective After the engine has been running for a few minutes the electric choke heater should begin to open the choke The choke will take longer to open fully in cold weather If the choke does not open it is either stuck or the choke heater is not working The choke mechanism can be freed up and maintained with Mouse Milk a high temperature penetrating lubricant If the engine surges or hunts does not stay at a constant RPM the cause is likely a gummed up carburetor or an improperly adjusted governor These conditions should be corrected If your multi meter has a frequency or a Hz range you can check the RPM by measuring the frequency of the 120 VAC at the outlet It should be approxi mately 62 Hz at no load and not go below 58
6. voltage is somewhat high or climbs the regulator is defective and needs to be replaced If the voltage immedi ately goes to 160 VAC on start up the problem is either the regulator or a loose connection at pin 2 of the regulator Check connections before replacing the regulator Q The voltage at the AC outlet is too low below 112 VAC at no load or goes down more than a few volts when a load is added What causes this A First make sure that the generator is running at rated speed This can be done with a multi meter that has a fre quency or a Hz range Make sure the slip rings are clean Check the connections between pins 4 and 5 or pins 1 and 5 on Microlite 2 8KW on the regulator as this can cause an output voltage of 55 60 VAC even with a good regulator When these causes have been eliminated the regulator is likely defective 6 Q With the generator running there is no 120 VAC at any of the outlets What is the problem A The AC circuit breaker s at the generator may be turned off or tripped Check the breaker s first Make sure that there is 120 VAC at the generator L1 L2 on the terminal block or pins 2 3 on the regulator plug If the circuit breaker is on there is 120 VAC at the generator and there is still no voltage at the outlets the problem could be a faulty transfer relay This device is located in the coach and is not part of the generator Its job is to switch the AC load from the commercial power to the
7. Hz at full load RV GENERATOR FAQs The following FAQ s apply primarily to Onan generators installed on many RV s but due to their general nature may apply equally well to other makes The information below is intended to help you get the best satisfaction from your RV genset and to enable you to find and correct some of the more common problems Certain models are not covered because of their complexity and the need for specialized servicing tools These include Quiet Diesel Models HDKAJ HDKAK and HDKAT Microlite Model KY Spec J and later Camp Power Model K YD Mobile Genset Models HGJAB and HGJAC Refer complex servicing to a qualified generator service facility Q When the start switch is pressed in the coach or at the generator nothing happens What could be the problem A The coach battery could be completely discharged or there could be a problem with a battery cable the control board or the wiring If the coach interior lights will not work the problem is likely the coach battery Check the battery and control fuse first If the lights work use the Troubleshooting Guide to isolate the problem Q When the generator start switch is pressed the starter makes a clicking sound but the engine does not crank What is the problem A Most likely the coach battery is almost completely discharged and needs to be charged or replaced There could also be a poor connection or a defective battery cable or starter solenoid If these causes ca
8. RCEDENCE Our Part Number 1720305 720305 _ VR305080905 VR3050897 3050826 A 3050911 A MED wasata 900 2764 1300 2843 300 3056 300 3687 300 3950 3003763 300 5268 300 3764 300 5342 300 3797 1300415 300 4320 300 4923 300 4506 1300 5002 _ 300 5002 01 2 3 4 300 4902 3005299 300 5046 AA _ I _ _ Gil level switch located inside of oil pan Gil level switch located on right side of oil pan JAS Oil pressure switch located on main bearing cover above oil filter 10 REGULATOR MATING PLUG REAR VIEW WIRING SIDE 300 2784 2943 ONAN ORIGINAL 11 300 3763 OR 300 3764 CONTROL BOARDS 300 4901 CONTROL BOARD 13 300 4320 CONTROL BOARD MATING PLUG J1 REAR VIEW WIRING SIDE 14 300 4155 CONTROL BOARD MATING PLUG P1 REAR VIEW WIRING SIDE CAUTION 600V 1 AMP DIODE 5 4 NOT CONNECT 12 VOLTS SUCH AS 1N40 s il DIRECTLY TO PIN 9 OVER A 200V PRESENT WHEN THE GENERATOR VOLTAGE BUILDS UP TO 12 VOLTS REGULATOR MATING PLUG REAR VIEW WIRING SIDE APPLICATION OF EXTERNAL FIELD FLASH USING DIODE CONTROL ASSEMBLY A1 300 5299 a DN 6 0 0 0 REAR VIEWS WIRING SIDE 16
9. RV GENERATOR TROUBLESHOOTING GUIDE CONTENTS RV Generator Troubleshooting Overview RV Generator FAQs Onan RV Generator Charts Applications Chart Test Information for Troubleshooting Regulator Pin Assignment Chart Control Board P N Supersedence Oil Press Level Switch Locations Onan RV Generator Control Board Regulator Illustrations Voltage Regulator Mating Plug 300 2784 2943 Control Board Onan Original 300 2784 2943 Control Board Replacement 300 3056 3687 Control Board 300 3763 3764 Control Board 300 4901 Control Board 300 4902 Control Board 300 4320 Control Board 300 4155 Control Board Application of External Field Flash using Diode 300 5299 Control Assembly Issued 6 08 Revised 1 09 RV GENERATOR TROUBLESHOOTING OVERVIEW HOW DOES MY RV GENERATOR WORK Note While this troubleshooting guide is applicable to most makes of RV Gen Sets there are many specific ref erences to particular Onan Models as these widely used RV Generators are the most popular brand we provide replacement control boards and voltage regulators for What the Engine Control Board Does The engine control board or module controls the ignition fuel pump fuel solenoid if equipped field flash and starter On LP models it controls the flow of LP gas to the throttle body Some models prevent the engine from starting if there is insufficient oil quantity Some models prevent continued running if there is insufficient oil p
10. at at the end of last season but now it has problems What could be the cause or causes A The generator was likely not exercised often enough or at all during the last period of non use A stabilizing addi tive may not have been added to the fuel see Q amp A above There could be latent corrosion damage from road chemi cals or wiring damage from rodents The problem could be simply a stuck oil pressure switch The problems experi enced could be for a variety of causes Generators need regular use or exercise in order to remain trouble free See next Q amp A below and also Troubleshooting Q How often should an RV generator be exercised and what is the procedure A All RV generators should be exercised at least once per month during periods of non use Make sure external AC power is disconnected from the coach and the coach battery is charged Start the generator and wait a couple of minutes for warm up longer in very cold weather Load the generator by plugging in a ceramic type portable electric heater approx IKW When the outside temperature is above 65F use the roof air conditioner to load the generator Allow the generator to run under load for 20 25 minutes Remove the load and run for another 2 3 minutes as a cool down period then shut down Q The voltage at the AC outlet is too high above 125 VAC at no load on start up or gradually climbs after the genera tor has been running for a while What causes this A If the
11. e control board is defective If the engine 2 CHECK SPARK If the engine cranks but does not start remove a spark plug and check for spark during cranking spark plug must be grounded Temporarily Jumper the ignition coil positive to the starter solenoid positive termi nal or jumper the BATTERY POSITIVE pin to the IGNITION pin on the control board If you now have spark there is a poor connection wiring damage or the control board is defective To determine if it is the control board check for 12 volts at the IGNITION pin during cranking Other problems such as dirty worn points or a defective coil can cause loss of spark On models where the oil level switch is hard wired to magneto KV Spec and low oil level or a stuck switch will inhibit the spark and prevent starting On these models it may be necessary to temporarily disconnect the oil level switch 1f 1t is stuck closed and not opening To check the level switch unplug the control board and verify that the MAGNETO KILL circuit on the control harness is not grounded Refer to the Troubleshooting Chart 3 CHECK FUEL SYSTEM If the engine cranks and has spark but does not start the problem is likely fuel related This can be confirmed by injecting a small amount of starting fluid into the air intake If the engine fires and tries to run it is starving for fuel Listen for the fuel pump running during cranking Check for 12 volts at the FUEL PUMP pin on the control b
12. generator when it is running Q What are slip rings where are they located and what is their function A Slip rings are two flat brass or copper rings located side by side on the rear of the rotor end away from the engine that provide a means of contact for the brushes The brushes run against the slip rings and carry the current field current required for magnetizing the rotor Q Why do the generator s slip rings require cleaning periodically A During periods of storage and a lack of regular exercise RV generator slip rings can become corroded particularly in areas near salt water Even with regular running a layer of oxide and brush residue can build up on the rings increasing their electrical resistance Proper cleaning such as with the Slick Stick Slip Ring Cleaning Tool available from our web site or parts department restores the running surface to like new condition This results in cooler running as well as extended brush and regulator life Dirty slip rings can cause overheating and premature regulator failure Q How can I determine if the slip rings need to be cleaned A A quick visual inspection can be done by looking through the cooling slots at the rear of the generator with a bright light The slip rings should appear as shiny clean metal You can also unplug the regulator and measure the resistance between pins 9 and 10 of the plug that was connected to the regulator If this reading is greater than 28 ohms cleani
13. h circuits The engine then cranks and starts Oil pressure and generator voltage build up within 1 2 seconds This causes the control board to keep sending 12 volts to the ignition fuel pump and choke heater while cutting off 12 volts to the starter solenoid and field flash circuits The start switch can then be released and the engine keeps running Some models differ slightly in operation On models equipped with magneto ignition KV Spec C F KY Spec A E the control board un grounds the magneto kill circuit Model KY Spec B E uses a fuel solenoid in addition to the fuel pump Models fueled by LP gas use a fuel shutoff solenoid valve instead of a fuel pump Several conditions can prevent the engine from starting running and are covered under Troubleshooting Normal Stopping Sequence This is what happens when you stop your genset Pressing and holding the stop switch for a few seconds causes the control board to cut off the 12 volts to the ignition and fuel pump and or fuel solenoid valve causing the engine to stop On models equipped with magneto ignition the control board grounds the magneto kill circuit Several conditions can cause the engine to stop by itself and are covered under Troubleshooting TROUBLESHOOTING Determine the control board part number from the board or from the Application Chart then refer to the Troubleshooting Chart for test information specific to that board This troubleshooting guide assumes that the person do
14. ing the work has basic mechanical skills and is familiar with electrical troubleshooting procedures using a multimeter Having a practical knowledge of RV generators is helpful but not absolutely necessary DISCLAIMER Generator servicing can present certain hazards such as cuts burns electric shock fire and exposure to exhaust Jumes Take suitable precautions Advanced Service And Parts LLC will not assume any liability for personal injury or damage to equipment or property as a result of using this Troubleshooting Guide Getting the Engine Running Before any evaluation of the controls regulator or generator can proceed the Onan engine must have oil and fuel be in running condition and the 12 volt battery charged The electronic governor 151 0752 on Models BGM and NHM Spec B and later must be functioning properly This guide does not cover engine maintenance and repair procedures please refer to the applicable Onan Service Manual for this information The most common engine problems are caused mainly by lack of use and or lack of regular monthly exercise and include the following e Low battery voltage because of insufficient charge worn out battery faulty cables partly broken or corroded or poor connections resulting in slow cranking and hard starting e Old or contaminated fuel that has gummed up the lines fuel filter and carburetor This can cause clogged jets mixture too lean and or a stuck carburetor float resulting in an impr
15. li cable Q Why does my generator run rough and or smoke even after it is warmed up A This can be caused by the electric automatic choke not opening choke stuck or choke heater not working an im properly adjusted carburetor too rich or a sticking carburetor float that allows excess fuel to enter the carburetor bowl Rough running can also be caused by fouled spark plugs Q Why does the generator RPM surge up and down and not stay at a constant speed A Surging is caused by a gummed up or improperly adjusted carburetor or an improperly adjusted governor Q My generator starts OK runs for a while and then shuts down Sometimes it can be re started after cooling for a few minutes What causes this A The most likely cause is fuel starvation This can be caused by low fuel level not getting gas vapor lock too hot gas is boiling fuel contamination water or dirt in fuel and or filter or a faulty fuel pump insufficient fuel pressure Models equipped with low oil level LOL switches will shut down the engine on low oil level Q What can I do to prevent fuel from deteriorating and causing problems during periods of non use A Regular exercise is a big help but a fuel stabilizer such as STA BIL should be added to the fuel at the start of the storage period Follow the manufacturer s recommendations and remember to run the generator long enough to get the treated fuel into the system Q My generator was running gre
16. n be eliminated then the starter itself may need service Q Why does my generator crank over normally but not start A The problem is either fuel or ignition related If the engine tries to run when a small amount of starting fluid is sprayed into the air intake it is a fuel problem The ignition can be checked by removing and grounding a spark plug Refer to the Getting the Engine Running section of the Troubleshooting Guide to isolate the problem Q Why does my generator start and then shut down as soon as the start switch is released A Most models require both oil pressure and AC voltage from the generator to keep running A lack of AC voltage can be caused by a variety of problems involving the control board regulator generator and wiring A stuck oil pressure switch can also cause this symptom The interaction between the various components of the system can be confusing during troubleshooting Use the Troubleshooting Guide to isolate the problem Q The start switch works at the generator but not from inside of the coach What is the problem A The remote start stop control is not connected to the control board Make sure the remote connector is plugged in to the control at the generator Check remote switch and wiring Q The start switch works from inside of the coach but not at the generator What is the problem A The start switch on the control board or control panel is defective Replace the switch or control board as app
17. ng is needed Q Is there a place where I can easily check for the proper voltages when the generator is running A Yes The 120 VAC and or 60 Hz frequency can be checked between pins 2 and 3 of the regulator or at any outlet and should be between 117 and 126 VAC at no load The field voltage can be checked between pins 9 and 10 of the regulator and should be 35 40 volts at no load and rise to about 60 volts at full load Freowewen zeso0e pzeso0v9s pzes 00 seo OGG VI MH oc ano pzesoos 766 096 956 pzes ooe seo ouss V gt NAW IEolueyooy _ 1680406 6629 0969 96 6629 00 seo ez v Hay smog 2680 5066 wN aon dlse9 SZ82 nA 25 045 9280606 vozeooevos poze ooe seo 89 Ja WHN 2810 50 9505 0959 9 9606006 Seo 59 Sd 3HN eolueuooy __6080G00 eozeo9evos eozeoos dl or WH 1898 vezz o9ew 9s 782 006 seo oy 3981 piuusa Waldvdv auvoa 9348 sawas SYOLVYANAD AY ZH 09 YO3 LYVHD NOILVINddV 7680 506 928050 106080 G0 1580 606 LSBO GO ozeo soc L0 6080 G0 0 6080 608 J uujojsuejl 401V10934 2640161 jeomeyos 2620 151
18. oard during cranking If there is no voltage the control board is defective The pressure and flow of the fuel pump and fuel filter can be checked by temporarily disconnecting the fuel line to the carburetor and jumpering the FUEL PUMP pin on the control plug to battery positive Take adequate precautions when han dling fuel If pressure and flow are normal reconnect fuel line Note If the generator has not been run for several months the carburetor float may be stuck closed and or the jets and needle valves may be gummed up by old fuel that has turned to varnish These conditions interfere with normal fuel delivery The automatic choke may be stuck closed or binding so that it does not open as the choke heater warms up On Models BGM and NHM spec B and later make sure that the electronic governor goes to full throttle one second after cranking begins Any of these conditions will prevent the engine from starting or running smoothly and must be corrected before proceeding 4 CHECK IF ENGINE KEEPS RUNNING The most common complaint is that the engine starts but will not keep running when the START switch is released This happens because the control board will not allow the engine to continue running if the generator is not producing voltage or if the oil pressure signal is not present See CONDI TIONS REQUIRED TO KEEP RUNNING on the Troubleshooting Chart for your model If the engine will not keep running do the following Al Generator AC Output
19. oper mixture too rich or too lean or flooding Weak spark and or fouled spark plug s causing hard starting and rough running Stuck automatic choke causing an excessively rich mixture and smoking Stuck oil pressure switch causing shutdown as soon as the start button is released Dirty air filter causing an excessively rich mixture and smoking Low oil level preventing starting on models equipped with low oil level switch Wiring harness damage from rodents chewing on the wires Corrosion of control board or connections from salty air or road chemicals FOLLOW THESE STEPS 1 CHECK OIL Check engine oil level before starting 2 GAINACCESS Remove panel or cover to gain access to the control board Some disassembly may be required The exact procedure depends on the model 3 CHECK BATTERY VOLTAGE Connect the negative voltmeter lead to GROUND and the positive lead to the positive battery cable on the starter solenoid and read the battery voltage The same reading should be obtained at the BATTERY POSITIVE pin of the control board A fully charged battery in good condition should read 12 6 to 12 8 VDC Charge the battery if necessary CHECK CRANKING Try to start the engine If it does not crank check the control fuse 5A Slo Blo except models with electronic governor 10A If the fuse is good jumper the positive battery post to the coil terminal on the start solenoid If the engine cranks there is a poor connection wiring damage or th
20. ressure See Troubleshooting Chart NOTE On models equipped with electronic governors BGM NHM Spec B and later 300 3764 control board the oil pressure signal to the control board comes from the governor module Additionally most models require a voltage from the generator to keep the engine running once it has started See Troubleshooting Chart All controls terminate cranking and lock out the starter after the engine has started The battery charging circuit is part of the control board on some models and external on others NOTE The controls used on Models KY Spec J KYD Spec A HGJAB and HGJAC are microprocessor based and combine the functions of the engine control and regulator in one module 300 5046 327 1413 and 300 5374 Because these modules are difficult or impossible to access without special tools they are not covered in these instructions What the Regulator Does When the generator is first started the regulator receives the field flash voltage from the control board and applies it to the generator field rotor to initiate AC voltage buildup in the stator After the generator output voltage builds up the regulator maintains it nearly constant within a few volts of 120 VAC under conditions of varying load It does this by sensing the 120 volts and constantly adjusting the DC field rotor voltage up or down as needed For example if you turn on a light the regulator would respond by increasing the field voltage only sligh
21. tly to compensate for the added load If you turn on a microwave oven or an air conditioner the regulator would increase the field voltage by a much larger amount in proportion to the heavier load The regulator has a built in protection circuit that reduces the output voltage of the generator if the engine is running too slow The purpose of this feature is to protect your appliances from receiving full voltage at the lowered frequency as this can cause damage to motors and transformers What the Bridge Rectifier Does The Bridge Rectifier is found on RV generators that do not have an electronic voltage regulator This will typically be found on BGE NHE generators spec A E built between 1985 1989 It serves two major functions field flash and field rotor voltage supply Upon starting the control board provides 12 volts DC to the field windings via the terminal of the rectifier Once oil pressure comes up another set of relays closes and opens accordingly on the control board and then the rectifier begins to work It now takes sensed voltage from the regulating transformer on the AC leads and rectifies it to DC voltage on the and terminals This is now the DC voltage that supplies the rotor of the generator Normal Starting Sequence This is what normally happens when you start your genset Pressing and holding the start switch causes the control board to send 12 volts to the ignition fuel pump choke heater start solenoid and field flas
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