That's good advice. What's happened since I started this thread was that the heat quit period. There's heat coming out of the exhaust, but with the thermostat set at 90, the metal of the registers started getting warm, but 4" above the registers the air was cold.
We've got the $110/hr repairman coming out Monday morning, again, to try and figure it out. Also our water froze again.
I think we need time with things working correctly to know what's going on. Right now, we don't know how much problems are caused by the fact that the nighttime temps are in the teens, and daytime temps barely above freezing, and what is actually problems with the 5th wheel.