I have a 2006 Lexington 255DS MH and the house battery has never charged off of the engine. My first guess is the charging relay is shot (see photo). I will replace that this week.
2nd issue, stupid error on my part (I think). The coach lights would work whenever the engine was running with to coach battery disconnected. Well not thinking i tried to start the generator and all the lights went out. Connected the coach battery and the lights worked and the generator started.
I looked for a blown fuse or relay and found nothing.
Any guess what failed?
Battery charging relay - Lexington 255DS 2006
, on Flickr