RV Furnace Won't Light? Common Causes and Fixes

An RV furnace runs on propane but needs 12 volt power for the fan, the control board and the igniter. When it won't light, the cause is usually power, propane, or a safety switch.

Check these first

1. Battery voltage. Low 12 volt power is the number one cause. The fan may spin but too slowly for the sail switch to close, so the furnace never tries to light. Below about 12 volts, charge the battery or plug into shore power.
2. Propane. Make sure the tank valve is fully open and the tank isn't empty. If other propane appliances (stove, water heater) also struggle, it's a supply problem. After a tank change, light a stove burner for a minute to purge air from the line.
3. Thermostat. Set it to Heat and a few degrees above the room temperature.
4. Fuses. Check the furnace fuse in the 12 volt panel and any fuse on the furnace board itself.

Signs and what they usually mean

• Fan runs, no ignition, then shuts off: low voltage, a sail switch problem, or air in the propane line.
• Clicks but no flame: propane supply, or a dirty or misaligned igniter (a job for a tech).
• Lights then goes out after a few seconds: often a flame sensor or limit switch issue.
• Nothing at all: thermostat, fuse, or power to the furnace.

Keep it working

• Check the exterior vent for wasp and mud dauber nests, a very common cause of trouble after storage.
• Keep return air vents clear inside.
• Make sure your propane and carbon monoxide detectors work.

If basic checks don't fix it, a certified RV technician should look at the gas valve, igniter and control board.