I can start it and it runs fine with a heavy load 20-30A. If I reduce the load, the voltage jumps from 120 up to 130v and then shuts down on over voltage error code 12. It won’t start or run with no or minimal load.
I don’t think it’s the governor, because when running with heavy load I can see the governor manipulating the throttle.
The field (slip rings and brushes) appear to be in fairly good shape, although one brush is longer than the other.
I suspect that it is the control board that regulates the field, perhaps shorted FET causing field to be at maximum, hence working okay when field current needs to be high.
I suppose it could be a gummed up primary or idle circuit in the carb such that there is little or no fuel when throttle is at low levels. That would explain no start/run with no load, but not the over voltage.
The control board is crazy expensive $2k from Onan. Apparently there are generic replacement boards I’m not sure how expensive.
I was going to buy this today, but my testing revealed the problem so the seller gifted it to me. It only has 200 hours of use.
I’m motivated to fix it because it does have some good points:
+ It’s fairly quiet
+ 30A @ 240V is enough for basics while the power is down.
+ Appears to be easy to service, filters, plugs, starter, etc all easily accessible.
+ supposedly good for 5000 hours
+ there is a gazillion of these out there, one in most RVs and bucket trucks etc.
Not so good: ……Cummins/Onan parts pricing.
