Nothing kills a camping trip faster than waking up at 3 a.m. in freezing temps with an RV furnace not working. Before you panic — or call a technician and pay $150+ just for a service visit — there's a good chance you can diagnose and fix the problem yourself in under an hour.
This guide walks you through the 10 most common reasons an RV furnace stops working, starting with the easiest checks and working toward more involved repairs. We've helped hundreds of RVers get their heat back on, and most issues turn out to be something simple.
Let's get your furnace running.
Why RV Furnaces Stop Working: The Short Version
Most RV furnaces use a forced-air propane system with a 12V DC blower motor. When the thermostat calls for heat, the blower spins up, propane flows, an ignitor sparks, and the burner fires. If any one of those steps fails, the furnace shuts down — often without any useful error message.
The most common culprits are: low propane, weak battery voltage, a dirty sail switch, a failed ignitor, faulty control board, or a clogged exhaust vent. Let's check each one.
10 Troubleshooting Steps: Start Here Before Calling Anyone
Step 1: Check Your Propane Level
This sounds obvious, but it's the #1 cause of a furnace that won't fire. Even if your gauge shows some propane remaining, the tank may be too low for the furnace to maintain adequate pressure — especially in cold weather, which causes propane pressure to drop.
What to do: Switch to a different tank if you have one, or check the gauge physically. If you're below 20%, refill before troubleshooting further. Also verify that your propane valve is fully open.
Step 2: Check Battery Voltage
Your RV furnace runs on 12V DC power for the blower motor, ignition board, and controls. If your battery is below about 10.5 - 11 volts, the furnace may refuse to start or will start and immediately shut down. This is one of the most overlooked causes of an RV furnace not working.
What to do: Use a multimeter to check your house battery voltage at rest. You want 12.4V or higher. If you're hooked up to shore power, make sure your converter is actually charging the batteries.
Step 3: Check the Thermostat
Before digging into the furnace itself, rule out the thermostat. Set it 5–10 degrees above your current interior temperature. Listen for a click or a relay activating. If you hear nothing at all when you turn the thermostat up, the thermostat itself may be the issue.
What to do: Check that it's set to 'Heat' (not 'Cool' or 'Fan Only'). Replace the thermostat batteries if it's a battery-operated model. If you have a multimeter, you can test for 12V signal at the thermostat wires. As a workaround, you can connect the thermostat wires together that come from the furnace which will signal the furnace to run continuously until it overheats.
Step 4: Inspect the Sail Switch
The sail switch is a small flap inside the furnace that only closes when the blower motor is producing enough airflow. If it's stuck, dirty, or bent, the furnace won't fire even if everything else is working perfectly. This is a very common RV furnace problem.
What to do: Turn off power to the furnace and access the blower compartment. Locate the sail switch (a thin metal flap on a hinge with a wire attached) and gently clean it with compressed air. Make sure it moves freely and isn't bent out of position.
Step 5: Check and Clean the Furnace Vents
RV furnaces have an intake and exhaust vent on the exterior of the rig. Mud daubers (a type of wasp) love to build nests in these vents, and a blocked exhaust will trigger the furnace's high-limit switch and shut it down as a safety measure.
What to do: Go outside and locate your furnace vents. They're usually on the lower side of the RV, covered by a louvered vent cap. Inspect them for nests, debris, or damage. Clear any blockage. This is a must-do inspection at the start of every camping season.
Step 6: Reset the High-Limit Switch
If the furnace overheated — even briefly — the high-limit switch may have tripped and stayed open. This is a safety device, so if it tripped, you want to understand why before you just reset it. Common causes include a blocked vent (Step 5) or restricted airflow inside the rig.
What to do: The high-limit switch is typically a small disc or button on the furnace burner assembly. Some reset automatically when cooled; others require a manual push to reset. Check your furnace manual for its location. If it trips again immediately, there's an underlying airflow problem.
Step 7: Test the Ignitor and Electrode
The ignitor electrode creates the spark that lights the propane. Over time, the electrode can get corroded, cracked, or positioned incorrectly. If you can hear the blower running but the furnace never lights (and then shuts off after 30 seconds), the ignitor is likely your problem.
What to do: Access the burner assembly and visually inspect the electrode tip for carbon buildup or cracks. Clean it gently with fine sandpaper or a wire brush. The gap between the electrode and the ground should be about 1/8 inch. If the ceramic insulator is cracked, the ignitor needs replacement.
Step 8: Check the Circuit Board and Fuses
Your RV furnace has a control board that manages the ignition sequence. A blown fuse on the board — or a bad board entirely — can cause the furnace to not respond at all. You may also have a fuse in your RV's 12V fuse panel dedicated to the furnace.
What to do: Check the fuse panel in your RV for a furnace fuse (usually 3A or 5A). Also inspect the furnace control board itself for burned spots, cracked solder joints, or blown inline fuses. A board that's been water damaged often shows visible corrosion. You can always use a multimeter on the board itself at the 4 contact points with the wires to see if voltage is being sent.
Step 9: Inspect the Gas Valve
If the furnace sparks but propane never flows, the gas valve may be stuck closed, faulty, or not receiving the 12V signal to open. This is less common than the earlier steps but worth checking if everything else looks fine.
What to do: With the furnace cycling, listen for a click from the gas valve when ignition fires. If you hear sparking but smell no propane at all, the gas valve isn't opening. You can test for 12V at the valve's solenoid with a multimeter. A gas valve that doesn't respond to voltage needs replacement.
Step 10: Test the Blower Motor
If the furnace doesn't produce any airflow at all — no blower sound — the motor itself may have failed, or the motor's thermal overload may have tripped. Blower motors typically last many years but can fail from moisture, debris ingestion, or bearing wear.
What to do: Check for 12V power at the motor leads when the thermostat calls for heat. If power is present but the motor doesn't spin, the motor is bad. If there's no power reaching the motor, the issue is upstream (board or wiring). A humming sound with no rotation often means a seized bearing.
Repair vs. Replace: How to Decide
Once you've identified the problem, the question becomes: repair it or replace the whole furnace? Here's a simple way to think about it:
|
Repair Makes Sense If... |
Replace Makes Sense If... |
|---|---|
|
The furnace is under 8 years old |
The furnace is 10+ years old |
|
The part (ignitor, sail switch, board) costs under $200 |
You've already repaired it 2+ times |
|
The heat exchanger and burner are in good shape |
The burner assembly or heat exchanger is damaged |
|
The failure is a single identifiable component |
You want more BTUs, efficiency, or features |
A replacement RV furnace from a quality brand like Suburban or Dometic typically runs $400–$1000 — far less than a shop repair job with labor. And installing it yourself is very doable with basic tools and a few hours.
Frequently Asked Questions
Why does my RV furnace start and then shut off after a few seconds?
This is usually caused by the sail switch not closing (indicating insufficient blower airflow), a blocked exhaust vent, or a propane pressure issue. The furnace initiates the ignition sequence, fails to confirm a flame, and locks out as a safety measure. Start with Steps 4 and 5 above.
My RV furnace blower runs but there's no heat — what's wrong?
If you can hear the blower running normally but no warm air comes out, the ignitor is usually the culprit. The burner may not be lighting, or propane isn't reaching the burner. Check Steps 7 and 9. You may also hear a clicking sound as the system attempts to ignite.
How do I know if my RV furnace ignitor is bad?
Visually inspect the electrode tip for cracks, corrosion, or heavy carbon buildup. If the ceramic insulator is cracked or the tip is worn down, it needs replacement. You can also test it by listening for the spark sound during the ignition cycle — no clicking means the ignitor or control board isn't firing it.
Can a bad battery kill my RV furnace?
Yes — absolutely. The blower motor and control board both require clean 12V DC power. Below about 10.5V, the furnace may fail to start or fail mid-cycle. Many RVers chase furnace problems for hours without realizing the real issue is a weak or discharged battery.
How often should I service my RV furnace?
At the start of every camping season — ideally spring. Clean the vents, inspect for wasp or mud dauber nests, check the electrode gap, and verify the sail switch moves freely. A 30-minute annual inspection prevents most in-field breakdowns.
Ready to Fix or Upgrade Your Furnace?
Whether you need a replacement blower motor, a new control board, or a complete furnace replacement, The RV Surplus carries furnaces and parts from Suburban, Dometic, Atwood, and more — often at clearance prices.