Originally Posted by Jammer
If it's 38 years old you really should replace the whole thing.
I'm not being a tightwad. I actually had planned on replacing it with a much newer Atwood.
But an RV appliance guy (marksrv.com) said that age alone would probably not wear out anything in the furnace and it has definately not been used much. The insides are mostly shiny. The baffles are free of rust.
The motor bearing is a good suggestion. I can just put power to the motor alone and see what happens.
Since i posted my question i've seen an actual schematic, there ain't much else it could be.