RV furnace not working: what fails, in what order, and what it costs

RV furnaces fail in a strict sequence, which makes them one of the easier systems to diagnose over the phone. The blower runs, then a switch proves the airflow, then the board calls for gas, then the igniter fires, then a sensor confirms the flame. Whatever step it stops at tells you what is wrong, and the great majority of these repairs land between $200 and $800.

Check this first (fifteen minutes)

1. Turn the thermostat up and listen. You should hear the blower start, run for fifteen to thirty seconds, then a click and a whoosh as the burner lights.
2. Nothing at all? Check the thermostat, the 12V supply, and the furnace fuse. Furnaces need good battery voltage; a bank sitting at 11.5 volts after summer storage will not run one properly.
3. Blower runs, nothing else? The sequence stopped at airflow proving or ignition. That is the sail switch, a blocked intake or exhaust, the igniter, or the board.
4. Look at the exterior vent. Mud dauber wasps build in the exhaust and intake tubes constantly in Arizona, and a blocked tube stops the sequence. This is one of the most common causes on rigs coming out of summer storage.
5. Lights then goes out after a few seconds? Flame sensing, or the high limit tripping because airflow is restricted. Check that interior return vents and floor registers are not blocked by furniture or storage.
6. Confirm propane. Other gas appliances lighting is the quickest test, and a nearly empty tank in cold weather can deliver poor pressure.

What is usually wrong

These sit on the pricing page alongside the $75–$150 trip fee and $125–$190 hourly labour.

Wasps, dust, and the Arizona storage cycle

Most October and November furnace failures trace to the same thing: the rig sat from May to September, and something moved into it. Mud daubers build in exhaust and intake tubes. Dust settles in the blower wheel and the burner. Rodents in storage lots chew wiring and nest in the plenum, which is both a repair and a fire concern.

The preventable version costs almost nothing: screens over the exterior vents, and a test run before you need it. Fire the furnace up for ten minutes in October when it is 80 degrees outside and the worst outcome is that you find a problem on a pleasant afternoon instead of at 2am in January.

The other reason it matters here

Visitors underestimate desert nights. The East Valley routinely drops into the 30s and 40s on winter nights, and an RV is a thin aluminium box with single-pane windows. It sheds heat fast. Snowbirds who arrive in October, run nothing but the AC for a month, then meet the first cold snap in December are the classic no-heat call, and they are all calling on the same night.

Duct losses, and the fix that is not a repair

If the furnace runs correctly but the rig never warms up, it may not be a fault at all. Common contributors: ducts that have come loose in the underbelly and are heating the basement rather than the coach, registers blocked by storage bins, a thermostat mounted on an exterior wall reading cold, and simple lack of insulation. Several of those are cheap to correct and none of them are furnace repairs, so it pays to rule them out before buying a part.

What to expect on the call

Tell us where the sequence stops, the furnace brand off the exterior panel if you can see it, and your battery voltage. That usually narrows it to one or two parts before anyone drives out. Furnace calls are handled on site across Mesa, Apache Junction, Gilbert, Tempe, Queen Creek, and Casa Grande, and the appliance repair page covers water heaters and the rest of the gas side.