I have the same problem with my Onan 5500 Gold Series. I even took mine in to have looked at and of course it didn't shut off for Dealer. I tried something when i got it back. With the gen running with no load on it shuts off by itself all the time. If i turn everything on in the trailer it won't shut off (go figure). I have heard though that if your batteries are completely charged the generator/ computer knows this and automatically shuts gen off. Does anyone know if this is true?