Steve - Sure sounds like thermostat. I had a different failure in mine and sent an email to
RV Comfort support. I described the problem and told them I would be comfortable changing it out if they wanted to just send the replacement directly to me. Return email said "it's in the mail". There was never any mention of the age of my unit, even though I was still under warranty at the time. They didn't even want the old one returned so I kept it as a spare. It's only failure was that it didn't call for help from the gas heat when needed.