Onan QG 4000 KY Spec R gas generator won't crank

[DavidEM]

My 2021 Thor Axis 24.1 has the Cummins QG 4000, KY Spec R generator. I went down to our storage yard in NW Connecticut to start the chassis engine and the Cummins generator to warm them up and circulate fresh fuel. The Cummins generator wouldn't crank. It acted like a dead battery but the house battery was good, showing 13.5 V (from the solar panel to keep it up while in storage). The chassis battery was also good and the chassis engine started right up, but Thor's rudimentary wiring diagram shows the generator starter being powered from the house battery.

There are four ways to start the generator: from the BMPro display panel, from a pair of switches in the bedroom, from a switch on the dash and on the generator itself. The first two are probably both being controlled by the BMPro Node (just like there are a few individual momentary contact light switches but all can be controlled by the BMPro itself). The dash switch acts just like the on engine switch (double throw momentary contact) with a light pulsing while cranking, so I am guessing it is in parallel with the on engine switch.

These two switches not working (and they are totally dead- no light comes on when starting or noise while priming) tells me that it the generator starting circuit is probably not getting any power. The generator starting circuit is fed by a 100 amp breaker near the batteries. I checked the breaker and it was on and there was voltage to and from it.

So the first thing I suspect is something pulled the 100 amp circuit loose from the generator. Maybe more likely there is a 5A fuse on the generator that protects that starting circuit (the two switches) and it may be blown. The generator started fine a few months ago when I put the coach to bed for storage and hasn't been moved since.

Any other ideas? I am going to wait till it warms up around here before crawling under and checking the 100A wire. So bear with me, this may take a while to sort out. Oh I just thought of something else. The generator starting circuit uses the chassis for ground, so maybe that connection has come loose so I will also check that as well.

David

[DavidEM]

So, I spent an hour or so at my RV trying to troubleshoot this problem. To summarize what post #1 said, the generator wont crank using either the on generator switch or the coach switches and there is power being delivered from the 100A breaker at the batteries.

The first thing I did was check for incoming voltage at the big lug on the starting solenoid- yes. Then I jumpered the two big lugs on the solenoid and the engine cranked. Then I jumpered from the big +12V lug to the far small lug on the solenoid and it cranked.

So, the starter and solenoid valve seem ok.

All of this seems to point to a 5A fuse protecting the starting circuit being blown, but... I am not sure there is such a fuse. The service manual I have goes through Spec G but mine is Spec R. Spec G has a fuse right over the on generator start/stop switch, but there isn't one on my Spec R and a thorough search didn't find one.

So does anyone have a Spec R service manual they could share- dmfeelingroovy@gmail.com or any ideas?

David

[Metalman]

I have two starting switches for the generator in the coach and one on the generator. Have you tried starting the generator with all switches? Do the switches illuminate during the priming sequence? (power to the switches?)

[DavidEM]

None of the switches work and none illuminate. I am taking it to a Cummins service center in Albany on Monday. It is still in warranty.

David

[Metalman]

It's fortunate that it's still under warranty. Good luck.

[DavidEM]

Yes, the only downside is a two hour drive to the Cummins service center in Albany. Hope they can fix it while I wait.

David

[DavidEM]

Well I got my generator fixed at the Albany, NY Cummins service center. Turns out there is no controls fuse on the newish Spec R generator. The problem was a dead control board and as luck had It, Cummins had one in stock. Once replaced, it worked fine.

And I am sure glad this happened with only a month or so left on Cummin’s 2 yr warranty. Otherwise it would have cost $1,000.

David

[16ACE27]

Originally Posted by DavidEM

Well I got my generator fixed at the Albany, NY Cummins service center. Turns out there is no controls fuse on the newish Spec R generator. The problem was a dead control board and as luck had It, Cummins had one in stock. Once replaced, it worked fine.

And I am sure glad this happened with only a month or so left on Cummin’s 2 yr warranty. Otherwise it would have cost $1,000.

David

[DavidEM]

Also I find it amazing that Cummins designs a generator with a $500 (parts cost) control board that fails enough for the Albany service center to have one on hand. I had a small diesel boat generator and it was all done with relays, so us mere mortals could fix it ourselves.

FWIW I don't think that the Cummins tech did anything more than I did- confirmed that the starting solenoid and starter worked and starting power was being supplied to the generator controls. The real test was replacing the control board. And it worked.

David