kjfmail,
The lights are probably 12V and have little to do with the APU (genset). Your APU has an electronic (digital) controller that controls both the engine and the generator output (iirc). I suspect that that part is failing. A replacement can be had, but I would suggest that you first purchase the service manual (if you can't find someplace to download it - I didn't even look for one) and then get someone that is electronic stuff savvy to look at it. If you have to buy a replacement from Cummins/Onan, remember to bring your duck tap to secure your wrist to your ankles. They are very proud of the parts that they supply.
Good Luck
Matt
