10K diesel Onan fault code 14

Disconnect everything you can from the other side of the main breaker, try again.

Could be a bad motor in something or a bad AC capacitor in the converter. Just grasping at troubleshooting straws here..

I think your problem is one of the loads in your DP. Turn off all the 20 or 15 amp breakers in your 120V panel. With generator running start turning the breakers back on. Your AC/ heat pumps have a time delay so you need to wait until the compressor kicks on before going to the next breaker.

I suspect your surging under load is lack of fuel. Could be a restricted fuel filter.

Richard

Lack of fuel is a very good recommendation and changing the fuel filter is the cheapest place to start unless it is almost new. Also, the fuel pump is a know problem area, enough so that I carry a spare one along with a filter.