An RV furnace not working is almost never one exotic failure. San Diego RV Center has serviced propane appliances on motorhomes, fifth wheels, and travel trailers from our El Cajon shop since 1990, and the cause is nearly always one of six things. Some you can check in ten minutes. Others you should not touch.
Start With the Battery, Not the Propane
This is the one that fools people. An RV furnace runs its blower motor on 12-volt power, and that blower draws real current. If your house batteries are weak, the furnace will click, the blower will try to spin up, and the unit will shut down before it ever lights — even with a full propane tank.
Owners hear the click, assume a gas problem, and start chasing the propane system. Check battery voltage at the terminals first. A healthy 12-volt battery reads around 12.6 volts at rest. Anything below about 12.0 is deeply discharged, and a furnace is one of the first things to quit. If your batteries are not holding a charge, that is a 12-volt system problem, not a furnace problem.
The Spider Problem
Spiders are attracted to the odorant added to propane, and they nest inside burner tubes. In Southern California this is common enough that we check for it as a matter of routine. A web or egg sac inside the tube chokes the air-fuel mixture, and the furnace either will not light at all or lights with a lazy yellow flame and shuts down on the safety.
The pattern is unmistakable: the furnace worked fine before the RV sat, and will not light after. If your rig has been parked for a few months and the heat suddenly quit, put this near the top of the list.
Six Things That Actually Fail
- Weak or dead house batteries starving the blower
- Obstructed burner tube, usually from spiders or debris
- Failed igniter, electrode, or a bad ground at the igniter
- Propane not reaching the appliance — empty tank, closed valve, or a regulator issue
- A tripped high-limit or thermal cutoff switch, often caused by blocked airflow
- A failed sail switch, gas valve, or control board
That high-limit item deserves a note. If your furnace runs for a few minutes then shuts off, then restarts later, it is usually overheating because airflow is blocked. Closed or crushed ducts, a blocked return air vent, or furniture pushed against a register will all do it. The switch is doing its job.
What You Can Safely Check Yourself
Confirm the propane tank is not empty and the valve is open. Verify other propane appliances light, which tells you whether the problem is the system or just the furnace. Check the thermostat is calling for heat and its batteries are good if it uses them. Make sure return air vents and floor registers are clear. Test your house battery voltage.
That is the end of the safe list. Anything past it involves the gas valve, the burner assembly, or the control board, and those are the components where mistakes cause carbon monoxide problems or fires.
Why This Is Not a DIY Repair Past a Point
RV fires are not rare. According to the U.S. Fire Administration, an estimated 4,200 recreational vehicle fires were reported each year from 2018 to 2020, causing an average of 15 deaths, 125 injuries, and $60.3 million in losses annually. Failure of equipment or a heat source accounted for 15% of them.
RV propane systems are built to NFPA 1192, the national standard for recreational vehicles, and repairs to a gas appliance need to keep the system inside that standard. A furnace that lights but burns incorrectly is more dangerous than one that will not light at all, because it runs while producing carbon monoxide and gives you no obvious warning.
When we service a propane appliance, we leak-test the system afterward. That step is not optional, and it is the one most commonly skipped.
What Furnace Repair Costs
A cleaning and burner service is the low end and solves a large share of no-heat complaints. Replacing an igniter, a sail switch, or a thermostat sits in the middle. A gas valve or control board is higher, and on an older furnace those parts can approach the cost of a replacement unit.
We diagnose first, then quote in writing. If the honest answer is that a twenty-year-old furnace is not worth a control board, we will say so — the same way we do with any RV appliance replacement, where the appliance is often the easy part and the wiring and clearances are not. Diagnostic time is billable and we tell you the charge before we start.
Heat out before a trip? Schedule an Appointment and we will get the furnace diagnosed properly rather than guessing at parts.
Prevention That Actually Works
Run the furnace once before storage and once before your first cold trip, so you find the problem at home instead of at 6,000 feet in Julian. Keep the exterior vent screened and clear. Have the propane system and appliances checked during annual RV maintenance, which is when we would catch a burner starting to foul rather than after it has quit.
Battery health is the other half. A furnace is a good early warning system for a house battery on the way out — if the heat gets unreliable before anything else does, look at the electrical system before you condemn the appliance.
Frequently Asked Questions
Why does my RV furnace blow cold air?
The blower is running but the burner is not lighting or is shutting down on a safety. Common causes are a blocked burner tube, a failed igniter, no propane reaching the unit, or low battery voltage that lets the blower spin but not sustain the sequence.
How much does RV furnace repair cost?
A burner cleaning and service is the least expensive outcome and fixes many no-heat calls. Igniters, sail switches, and thermostats are mid-range. Gas valves and control boards are the high end. We give you a written estimate after diagnosis, before any work starts.
Can I run my RV furnace off the generator?
The furnace itself runs on 12-volt power and propane, not 120-volt. Running the generator helps indirectly by charging your house batteries through the converter, which is often exactly what a furnace with weak batteries needs.
Do you service furnaces on all RV brands?
Yes. We work on the major RV furnace manufacturers across motorhomes, fifth wheels, travel trailers, and toy haulers, and we serve owners throughout San Diego County from our shop off Interstate 8 in El Cajon.
Ready to Get Started?
A furnace that will not light is usually a cheap fix caught early and a dangerous one ignored. Let us diagnose it properly and leak-test the system while we are in there.
Schedule an Appointment or call us at (619) 561-3531.