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Old 10-29-2002, 09:27 AM   #1
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Question Generator onan

For the last six months I have been trying to figure out why my gen won't run,so I took it to a electric motor shop. They said I had a bad armature, then told me the price to fix it over 2000. When I told them sorry, just forget it, they then wanted to know what I wanted for it. Didn't sell it. Now back at home and reenstalled in the motorhome the silly thing started and ran for anout a minute. Now it will start but when you let go of the start switch it stops. I disconnected the oil pressure switch to see if that was causing the problem it still won't run. This is my question, if the armature is bad why did it run, if the armature is bad why does it start? A friend told me that his onan gen had my symptoms, cranked slowly but had a good battery and he replaced the brushes and it runs great now. Could bad brushes cause this problem? took them out and looked at them they looked fine, but I don't know a good one from a bad one. Could an open relay cause this problem or what about an open reverse current diod? If so how do you check them with a meter? Some advice please.
(The last thing I want to do is take it back to Onan and give them more money I am tired of making boat payments for the mech.)
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Old 10-29-2002, 10:51 AM   #2
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What model generator?

Sounds like you should have gone to a small engine shop. What brushes are you talking about, the starter brushes or the generator brushes? If you hold the switch and it is running, is it putting out AC voltage? There is an engine and a generator, and unless the generator is also used to start the engine it sounds like you are working on the wrong end.

The start-stop system on mine (4 kw Onan Emerald) is ground to start, ground to stop. Make sure you didn't pinch the control wires when you reinstalled.

Check a diode by putting an ohm meter across it. Then reverse the leads. One way should be short, the other open. If so it is good. If you get the same reading both ways it is bad.

A relay can be normally open or normally closed. Use the ohm meter again, no voltage on the contacts. When activated it should change state if good.

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Old 10-29-2002, 01:10 PM   #3
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It is an Onan 1982 6500 GenSet. The generator is the starter. It uses a seires field to turn over and start, no bindex type starter on it. As for the producing AC I am not sure I never held it on for more than a thirty or forty seconds, I was afraid to.
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Old 11-02-2002, 11:46 AM   #4
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I checked the diode reverse current one and it seems good. But the relay seems to be different question. It is always hot at contacts 3 but not 2 or 4 or at the same time. I have not figured that out yet. The book explains it but not very well at least not well enough to actually find and correct.
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Old 11-02-2002, 12:13 PM   #5
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I still think you might be on the wrong end of this. Have you check the 120v out? Stick the probes from a VOM in a plug you can see from the start switch or plug a lamp in, start it and see if the generator is working.

On the relay, what do the different terminals go to? Mine is ground to start, that would make the terminal for the coil always hot, you ground the other side throuh the switch to activate.

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Old 11-26-2002, 11:57 AM   #6
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Onan Generator

I seem to have the same problem - but it is of recent origin -- generator starts nicely but shuts down as soon as you release the start button. The generator will continue to run if you hold the start button on but the "gen" light never comes on and it never sounds like the generator load kicks in.

This is an Onan 4kw BGE/BGEL unit in a 1990 25 foot motorhome. It has maybe 40 hours on it.

Any sort of relay is not easily visible - in side the box where the start button is on the unit is a small circuit board - all connections look solid and the fuse is OK.

Any suggestions will be much appreciated.

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Old 11-26-2002, 12:51 PM   #7
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Found this guide to troubleshooting- hope it helps. (sorry about the format problem)
Troubleshooting Onan Generator Sets ----Cummins inc
Problem Possible Causes Checks/Solutions
Fails to Crank 1. Low battery2. Bad batteryconnection 3. Blown fuse
1. Check battery fluid level 2. Clean and tighten all battery and cable connections 3. Replace fuse on control panel
Cranks Slowly
1. Low battery 2. Bad batteryconnection 3.Incorrect oil viscosity 1.Check battery fluid level
2. Clean and tighten all battery and cable connections
3. Replace with rec. viscosity oil
4.Disconnect load before Starting
Cranks But Won't Start
1 Fuel below GenSet pickup level in tank
2. Fuel supply shutoff valve closed
3.Carbon deposits on sparkplug(s) .
4 Low oil level
1. Add fuel 2. Fully open fuel supply valve 3. Remove spark plug(s) and replace 4 Add oil if necessary
Exhausting Black Smoke
1.Rich fuel mixture
2. Dirty air filter
3. Choke stuck or misadjusted
1. Turn main fuel adjustment 1/8 turn (clockwise)
2.Replace air filter 3. Contact Onan Service

Unit Runs Then Stops,or Stops When Driving Around Corner
1 Low on fuel
2.. Low oil level
3.Excess oil level 1.Refill fuel tank
2 Add oil if necessary
3 Reduce engine oil level

Unit Starts and Runs, Then Stops When the Start Switch is Released
1.Low fluid levels
2.Possible overheating
3. Other functional problem
1.Check and bring all fluid levels up to the appropriate level.
Check for blocked air flow or
other possible causes of overheating

Unit Runs Then Surges
1 Loose or worn spark plug leads
2.Defective ignition coil, wiring, or control components
3.Faulty spark plug
3.Governor out of adjustment
4.Combustion air preheat malfunction 5.Carburetoricing

1.Check spark plug leads at spark plug and ignition coil
2. Remove spark plug and clean or replace
3. Move carburetor preheater to the winter position
4.Turn main fuel adjustment out 1/8 turn(counter clockwise)

Circuit Breaker Trips
1. Overloaded circuit
1. Turn off some of the electrical load, and reset the circuit breaker.
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