Onan Generator won't run

[JJH3rd]

OK, I did my research (here, Google and Yahoo) to see if anyone had any suggestions as to how to deal with my generator problem. Here's what I've done & discovered:

The problem: the generator starter works to get it started (the starter disengages when the motor 'catches') and it runs as long as I press the "Start" button (rocker switch), but when I release the "start switch, the engine stops. Before this situation, I usually kept the start switch pressed for less than 10 seconds and the light in the switch would change from flashing (starting) to continuous (running). Now it never makes the change from starting to running even after +20 seconds of "starting".

The generator is: getting fuel, the carburetor is clean & the float works, the spark plugs are OK and are delivering spark, the oil level is OK.

Just because, I dropped all powere to the coach (battery disconnect) and checked for any open fuses (AC & DC) and found all were OK but that didn't have any effect on the situation.

ANY SUGGESTIONS AS TO WHAT TO DO NEXT (other than take it to the local Onan service place), WOULD BE GREATLY APPRECIATED.

[Dave78Chief]

The first step with a 7HGJ Series Onan Generator is to read the Fault Code as described in the Troubleshooting section of the Operators manual. Are there any Fault Codes?
http://www.cumminsonan.com/www/html/...s/983-0101.pdf

Dave

[rgvtexan]

Did you check the oil level? Do you get any fault codes after the start attempt?

[JJH3rd]

Thanks I'll see what the fault code is tomorrow morning.

Yes the oil level is fine (about 3/4ths to the full line).

JJ

[JJH3rd]

OK. Got two fault codes: 34 then 47. The first one isn't in the service manual, the second says ignition fault. I called Bob at JTF Moble in Conyers GA and he suggested that I checked to see if the belt that drives the generator was still there and that the generator was turning. I did this by pulling the brushes and looking in the opening at the belt while starting the motor. It turns out the belt was fine an the brushes have plenty of life left in them.

Rechecked the fault codes and still got 34 (once) and then 47 (over & over).

Talked with Bob again and decided the control board was putting out bogus codes: 34 - unknown, 47 - ignition fault - NOT LIKLEY because the gas motor works fine.

The first image shows the location of the brushes and the others show what it took to remove the control board:

Looked on the Internet and found that anyrvparts.com had the board at $317.89+shipping so ordered one and it should be on its way today or tomorrow. Other places have the same board at $389 and $399. Go figure.

I'll follow up with the results after I install the board. JJ

[JJH3rd]

One final image with the control board removed.

More to come. JJ

[Dave78Chief]

Here is the service manual:
http://www.cumminsonan.com/www/pdf/m.../983-0501D.pdf

As shown on page A-1, most everthing feeds into the control board (brains of the unit).

Dave

[TLGPE]

JJ, I've never used an ONAN, bit just a suggestion; check the rocker switch itself. If it's like others, you push one end to start and the other end to stop the engine. If the switch is faulty, it could be making contact to "ground" the ignition and stop the engine. The switch could also be failing to keep contact with the supplied ignition voltage. Just something to check before you get too deep into changing out expensive parts.
Tom

[Dave78Chief]

JJ,
For reference, with this model generator Onan has migrated to what amounts to a computerized system (control board you ordered). Think in terms of a car computer. Everything goes to/from the computer. Additionally, Onan no longer used points or even electronic ignition. Each plug circuit is an indepent magneto circuit akin to a lawn mower. Magnet on flywheel passes through mounted coil generating a spark in plug. The computer simply opens and closes the ground path circuit to turn ON/OFF the engine. Simple but effective design with the only thing that can fail is the plug or the computer board.

Dave

[Donlock]

I had that issue ? Does the switch work inside the same.?
I ordered new carb, new board, brushes, oil switch, AnyRv parts
excellent to deal with and prices cheaper.
So found broken wire from gen to inside switch fixed it, put new carb on
but be sure you check where the gov spring is set. After i did that it still
wouldn't work then all of a sudden it started working. Go figure just throw
money at it ,and it will go hasn't stopped working so far :-)
Don

[ahicks]

It's been a while since I've worked on one of these, but back then we had some trouble with the oil pressure switches causing that same problem? No oil pressure, no ignition when you let go of the start button. Could be oil of the wrong viscosity (back then) or a bad switch. We used to change the oil first....

[JJH3rd]

I wondered about the various sensors when I reviewd the trouble shooting dierctions under the code 47 - ignition fault. Bob at JTF pointed out the gas engine was starting and when I removed pressure from the start switch, the engine shut down. The problem was running, not starting.

The control board is on its way, I'll post an update when I receive and install it. JJ

[JJH3rd]

Put in the new control board and still no joy

The symptoms did change.

Now after cranking and starting the engine shuts down while I'm still holding the start switch closed. Now the fault code is 41 - Generator rotor fault.

I think I've reached the end of my ability to repair this unit in my back yard. I looks to me like the genset will have to come out of the RV to get to the generator. I'll give Bob at JTF a call Monday to see if he has any words of wisdom. JJ

[JJH3rd]

Yep, there's a visit to JTF in the not too distant future

Bob gave me a few "it could be's" - It could be a slipping drive belt from the gas engine to the generator or the tensioner for the belt (see earlier post - the belt and shaft of the generator was turning), it could be some part of the guts of the generator; only removing the genset from the unit and working on the generator will tell. Right now I estimate about $1K to repair at the high end. Replacement Cummings/Onab getset is a little less than $5K,

I am planning to take the unit into JTF the end of July or in August so the next update will be over a month away. JJ