October 5, 2026
Why Your RV Furnace Won't Stay Lit on Cold Nights
Fall and early spring camping in Indiana and Illinois can bring nights near freezing. That is exactly when an RV furnace likes to light, run a minute, and shut off, leaving you under extra blankets. The good news is that the cause is usually one of a few things, and several of them you can check yourself.
How an RV furnace works, briefly
Most RV furnaces follow the same sequence. The thermostat calls for heat. The blower starts and pushes air through the combustion chamber. A switch confirms airflow. The control board opens the gas valve and sparks the igniter. A sensor confirms flame. If any step fails, the board shuts the furnace down for safety and may try again.
Knowing that sequence makes troubleshooting much easier. A furnace that will not stay lit is usually failing one of those checks.
Low battery voltage
This is the most common cause, and it surprises many owners. The furnace runs on 12-volt power even though it burns propane. The blower motor draws a lot of current. If your batteries are low, the blower slows down, the airflow switch does not close, and the furnace shuts off. In cold weather batteries also lose capacity, which makes the problem show up more at night.
Check your battery voltage with a meter if you have one. If it is low, plug into shore power or run the generator and see if the furnace behaves. If it suddenly works, the problem is your batteries or charging, not the furnace.
Propane supply
A tank that is nearly empty can still light a stove burner but not support the furnace for long. Cold weather lowers tank pressure, too. Check your tank level. If you recently changed tanks, light a stove burner for a minute to purge air from the lines before running the furnace. Weak, yellow, or lifting stove flames can point to a regulator issue.
Airflow problems
The furnace needs strong airflow to stay running. Blocked return air vents, furniture or bedding pushed against vents, a crushed duct, or closed floor registers can all reduce airflow enough to trip a safety switch. Walk through the RV and make sure all heat registers are open and unblocked, and the return air grille near the furnace is clear.
Blocked exhaust or intake
The outside vent on the side of the RV lets the furnace pull in combustion air and push out exhaust. Insects, wasps, and mice like to build nests there, especially after storage. Look at the vent from outside with a flashlight. Do not stick anything into it while the furnace is running, and never cover it.
Things you can safely try
- Charge or connect to shore power to rule out low voltage
- Confirm propane level and purge air by lighting a stove burner
- Open every heat register and clear the return air path
- Look at the outside vent for nests or debris
- Reset the thermostat and let the furnace try a full cycle
When to stop and call
If you smell propane, see soot around the outside vent, hear loud banging at ignition, or the furnace keeps failing after you have ruled out power and propane, stop using it. Inside the furnace are the sail switch, limit switch, igniter, and control board, and testing them takes the right tools. A malfunctioning furnace is not something to keep cycling just to stay warm.
Also remember to keep your CO detector working. It is your safety net any time you are burning propane inside the RV.
If you would rather have it done right without the guesswork, call or text Mat at (855) 949-6107. He comes to your home, campground, or storage lot.
