Onan 4000 Generator circuit board

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kps7987

New member
Joined
Jun 12, 2022
Posts
2
Location
Allentown, PA
We went camping this weekend and were using our generator several times. We used it for air conditioning, microwave and blow dryer but never at same time and for periods of time from 30-45 minutes. As we turned in on for the night Cool down there was a small pop, generator engine shut down but made a constant buzzing sound and smell of smoke. I looked and the urethane around the circuit board was melted in one corner. I came home and tested all of the systems with shore power and everything works as normal. I can replace the circuit board pretty easy but concerned another issue caused this. Can a circuit board in urethane just go bad after 11 years in this manner or should I look for other causes. Already checked connections and for bare wires with no results. BCE90F46-FCA2-45D1-9B51-22008A36B248.jpeg
 

jackiemac

Site Team
Joined
Feb 22, 2016
Posts
7,315
Location
Scotland
Hi and welcome. Unusual that you've not had any responses.

That looks scary and could have been a problem.

Hopefully you have got it resolved but if not please let us know and maybe someone will have some ideas.
 

Isaac-1

Well-known member
Joined
Dec 3, 2016
Posts
5,858
Location
SW Louisiana
I don't know the history on your generator, but tarnish buildup on the slip rings due to disuse of the generator for long periods of time can cause the voltage regulator part of that control board to overload and fail due the added resistance in the circuit, this is part of the reason it is suggested to exercise your generator for at least 15 minutes once per month.
 

kps7987

New member
Joined
Jun 12, 2022
Posts
2
Location
Allentown, PA
I checked with Cummins and tan every system on shore power. Everything seemed to work ok and the Cummins mechanic said he has seen circuit boards go in this manner due to age. I replaced circuit board and did visual inspection for bare wires and fuses and everything seems to run as it should now. Bought the circuit board from Flight Systems for $150 less than Cummins direct.
 

Matt_C

Well-known member
Joined
Mar 4, 2019
Posts
673
Location
SE - Mich
KPS,
Thanks for closing the loop on this one. I didn't bother to post anything because our Onan is 40 years older than that and looks nothing like it. Glad Flight Systems could help.
Matt
 
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