Onan Marquis Gold 5500 Generator Just Quit

[kdbgoat]

Problem found! 

Thanks everyone for your input.

I did the crank test and found the field resistance steady at 29.3 ohms.

It kept bothering me that with the 30A breaker off the genny would run, but instantly die when turning the breaker on.

I disconnected the wire to the motorhome from the breaker and alligator-clipped a 100 W trouble light to the terminal. When I started the genny and turned on the breaker it kept running and illuminated the lamp. Hmmmm.

The AC cable from the genny goes to a four-square junction box and then to the transfer switch. The transfer switch lives in a 5" cube attached to the back of the AC/DC load center which lives under the bathroom lavatory. It was a struggle to get it out. I had to unhook numerous wires.

Once access was gained the problem was obvious. The hot wire from the genny went to a connection block. The connection must not have been tight and overheated, melting the connecton block. This allowed the wire to touch the grounded mounting bracket.

It will take some time to put it all together but the fix will be free.  I can't help but wonder how many parts and hours a dealer would have thrown at it before finding the problem.

Tom

"Told ya" ;D I get lucky on diagnosis once in a while.

Glad you found the problem and got it fixed.

 

[Heli_av8tor]

Yes you did. What threw me was that when closing the breaker there was no indication that there was a short. The genny controller shut it down before the breaker could react.
I?ve closed more than one breaker on a shorter circuit and heard the arc and breaker snap open. No such feedback on this.

 

[John From Detroit]

I agree that's a new one on me too, a short.. I'd have thought the breaker would well Break (the circuit that is) but I guess it has a bit of "Hang time" (most do)....

in another system I have a device that likes to blow fuses. So I switched to a breaker precisely due to that short delay.. And promptly blew the controller.. thankfully that was an eaxy no-cost fix (Just needed a bit of solder and a strand of scrap wire and of course about $150 Dollars worth of Terchniciasn timer.. but bering as I am the technician that weas $0.00) Works great now.

I now use the circuit breasker and a relay that can handle far more current. Last test was good.