We have had a few repairs this summer where customers have removed the furnaces from their RV, and brought them into our shop for repairs. We cleaned out the combustion chamber and adjusted the spark ignitor and then bench tested the furnace for results. Everything appeared to be operating as intended when we performed our bench test.
The customer picked up the furnace and re-installed it into their RV only to find that they were having the same issues with performance. We asked them to drop off the RV with the furnace installed so that we could test the furnace in place and sure enough, we found the problem. It was not the furnace at all. Actually there were a few things that we found:
1. There was an oil like substance in the propane lines that was restricting the delivery of propane to the furnace along with all of the other propane appliances. Old or stale propane can leave this oily build up in the propane lines that will cause performance issues with all of the appliances.
2. The propane 2 stage regulator can also cause a problem with the operation of all of the appliances if it is not delivering the proper output pressure. Sometimes this can be adjusted on the regulator, but this should only be performed by a certified RV Technician.
Before you call for a site service call or remove your furnace for repair, check to see if any of the other propane appliances have performance issues. A service call may not resolve the issue.