Are you hoping your RV furnace will fire up when temperatures drop? Or do you want to know for sure that it will?
The RV furnace is one of the most neglected appliances in an RV. It sits unused for months at a time, yet most people expect it to run perfectly the moment they flip the switch. Unfortunately, dirt, insects, vibration, and simple wear-and-tear can cause furnace failures at the worst possible time—when it’s already cold.

In this Tech Tip Tuesday, Sue, the NRVTA’s instructor for water heaters and furnaces, explains the essential maintenance steps you should take before winter arrives.

To make it easy to remember, she uses one simple acronym: H.E.A.T.

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H.E.A.T: The 4 Steps to RV Furnace Maintenance

H — Hoses & Vents (Keep Your Furnace Breathing)

Your RV furnace must breathe. Proper airflow begins at the vents and continues throughout the ducting.

Start with the exterior exhaust vent

The furnace exhaust vent is one of the most common problem areas. Insects love the smell of propane—especially wasps and mud daubers—and will often build nests inside the vent. Dust, debris, and even small animals (frogs included!) may find their way inside.

Make sure:

• The vent is clear of insects, nests, and blockages
• No dust, dirt, or debris is restricting airflow

Check your ducting and registers

Most RVs use lightweight, flexible ducting. Over time:

• Debris can gather
• Registers become blocked
• Floor vents (especially) get covered by rugs

If you’ve installed temporary screens or dryer sheets during storage to prevent debris from falling into the ducts, remove them before running the furnace.

A quick vacuum around your floor vents goes a long way.

Your furnace needs full, unrestricted airflow—always start by giving it a clear path to breathe.

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E — Electrical Flow & Components

Your RV furnace operates on 12-volt DC power, making wiring and electrical components critical to proper operation.

Inspect the wiring

Road vibration and rodents can damage wiring over time. Look for:

• Chewed wires
• Melted or overheated sections
• Cuts caused by vibration or sharp furnace housing edges
• Corrosion at connectors

Clean and tighten all connections as needed.

Inspect your furnace components

Several key components rely on proper electrical flow:

• Control board
• High-temperature limit switch
• Gas valve
• The sail switch (often the first to fail)

The sail switch is especially important—it detects airflow and prevents ignition if airflow is too low. Because it collects dust, pet hair, and debris, it often needs cleaning or replacing.

Important: Dometic furnaces use four different types of sail switches. Always buy the one designed for your specific model.

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A — Airflow (The Lifeblood of the Furnace)

Airflow is everything. Without proper airflow, the furnace won’t ignite—and for good reason. The sail switch must detect enough airflow to signal the control board that it’s safe to operate.

Start with the blower motor & wheel

Inside the furnace housing, the blower wheel can:

• Collect dust and debris
• Lose fan blades
• Become unbalanced
• Stop spinning freely

Remove the cover, inspect the fan wheel, and spin it by hand. It should rotate smoothly without rattling.

Clean the return air area

Your furnace pulls return air in through a low-mounted intake. That return air brings everything with it:

• Dust bunnies
• Dog and cat hair
• Construction debris
• General dirt buildup

Vacuum this area thoroughly. This is the one piece of maintenance you should do frequently.

Never install a filter in front of the return air intake. A furnace needs unrestricted airflow, and filters can block enough air to prevent ignition.

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T — Test (Make Sure It Works Before You Need It)

Once your furnace is clean, inspected, and reassembled, it’s time to test it. Here’s what a proper operating sequence looks like:

1. Thermostat calls for heat

Turn the heat setting up so the furnace receives the signal.

2. Blower motor starts (15–25 seconds)

Cold air blows first—this is normal.
This purge cycle:

• Clears residual gases
• Gives time for the sail switch to close

3. Trial for ignition

You should hear: tick tick tick tick
The furnace attempts ignition.

4. Flame ignites

Once lit, the furnace begins heating and pushing warm air through the ducts.

5. Furnace shuts off

When the thermostat is satisfied, the flame stops—but the blower continues for another 45–90 seconds to clear residual heat.

If your furnace follows this sequence smoothly, it’s in good working condition.

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Stop Hoping—Start Knowing Your Furnace Will Work This Winter

A neglected furnace is one of the top causes of winter RV emergencies. With the H.E.A.T. process—Hoses, Electrical, Airflow, Test—you’re no longer hoping the furnace will work when the cold snaps hit.

Now, you’ll know.

And if you want to learn furnace maintenance in-depth—or start a business helping other RVers—check out the National RV Training Academy, the largest hands-on RV training academy in America.

RV Furnace Maintenance