You probably got one of the last bad Dometics that was recalled. I had a bad one in a 98 SB. I think 97-03 were the recalled years. I got a rebuilt and the guy already knew where Dometics screwed up and he had the fix for it before Dometic admitted what the problem was. Your 04 is probably like my 08. The basement is a return air plenum and I spent a day fixing the shrunken gaskets on the basement doors and sealing all the plumbing/electrical penetrations from the basement to the under belly and the heating got MUCH better. Craig