Propane Furnace Inspection

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Well-known member
Aug 19, 2006
When I first used the furnace last month, the smoke detector went off.? I figured since the unit sat on the dealer's lot for 10+ months, that wasn't so unexpected.? I have the same problem with my home furnace after it sits idle from April to December.

Took it out again this past weekend and the smoke detector did not go off the first night, but did the second night.? I did change the direction one of the vents was blowing inbetween.

While you probably wouldn't say the air smelled like smoke, you can tell a definite difference in smell when the furnace is running.

How hard is it to take apart to the point where you can inspect it or clean it??

I assume the first thing to check is the two outside vent channels (inlet & outlet?) for blockages like mud dauber nests.? Can that be done with a flashlight, or is disassembly required?? [I did buy the anti-mud-dauber screens several weeks ago and installed them, but did not inspect inside the furnace.]

If those look clear, what do you check next?


Well-known member
Sep 29, 2006
Jackson, Michigan
I had the same problem when the stuff in my trailer was new. After I used the stove & furnace a bit everything was OK.

Gary RV_Wizard

Site Team
Feb 2, 2005
At our Silver Springs FL home
The outside vent channels are easy to inspect from the outside (just pull the cover) but hopefully are not the source of your problem. The inlet and exhaust are supposed to be completely isolated from the inside air circulation - the inside air is heated via a heat exchanger inside the furnace.  No exhaust should be getting inside the rig and no combustion air is drawn from inside the rig.  A failed gasket in the furnace could allow that, though, and is a very serious condition that must be corrected before any further use.

There are two designs for the outside of the furnace. In one, there is just a small cover for the two air tubes, inlet and outlet. In the other, there is a fairly large cover on the outside wall that gives access to the back of the furnace when removed. The large cover has gaskets that prevent mixing on inside air with the exhaust & inlet tubes, so you have to be very careful not to damage those gaskets and to get them properly positioned when re-installing the cover.

Usually internal smells are caused by dust, insects or rodents getting into the furnace ducts by which warm air is circulated to the RV interior. Critters have been known to crawl up the ducts and nest inside the house side of the heat exchanger, where they or their leavings get toasted when the furnace comes on. Covers on the duct outlets are supposed to prevent mice and such from doing that, but insects, blown dirt/dust, etc. can readily get in.  You should be able to uncover the furnace from the inside (often by removing an interior panel or grill) so you can see where the heat ducts attach to the furnace. They are just held on with hose clamps, so they are easy enough to remove and inspect/clean, if you can mange to wiggle into wherever they are. You can also vacuum out the heat exchanger plenum through the duct outlet holes.  All this to be done with furnace off, of course.
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