RV Furnace Failures in the Pacific Northwest
Snohomish County's shoulder seasons — fall and spring — are when furnace failures are most disruptive. Temperatures at Kayak Point, Lake Goodwin, Wenberg County Park, and along Highway 2 toward Stevens Pass drop into the 30s regularly from October through April. A furnace that worked fine last spring often won't fire after sitting idle all summer: the sail switch corrodes, the electrode collects carbon deposits, and the ignition board's capacitors age.
Common RV Furnace Failures — Quick Diagnosis Guide
| Symptom | Most Likely Cause | Typical Fix |
|---|---|---|
| Blower runs, no ignition, shuts off after 30–45 sec | Sail switch fault or ignition board lockout | Sail switch replacement or board reset/replacement |
| Furnace doesn't respond at all (no blower) | Dead 12V supply, blown fuse, or failed board | Fuse check, battery voltage test, board diagnosis |
| Furnace ignites briefly then shuts off | High-limit switch trip, propane pressure fault | Limit switch test; propane regulator check |
| Furnace runs but heat output is weak | Partially clogged burner or restricted exhaust | Burner cleaning; exhaust port inspection |
| Furnace smells like propane when running | Combustion air leak or cracked heat exchanger | Heat exchanger inspection; do not operate until repaired |
What We Repair
1 Sail Switch Replacement
The sail switch is the number-one furnace repair we perform in Snohomish County. It's a lightweight plastic or metal flap inside the blower housing that proves airflow before the gas valve opens. When it sticks, corrodes, or breaks, the furnace locks out after the blower starts. We carry Dometic and Suburban sail switches on the truck and typically complete this repair in under an hour.
2 Ignition Circuit Board Replacement
The circuit board controls the ignition sequence — blower startup, gas valve timing, electrode spark, and flame verification. Boards fail from age, moisture intrusion, and power surges from a faulty converter. We test the board's output signals before condemning it, because a board that appears dead is sometimes a fuse or power supply problem upstream. When the board is the fault, we replace it with OEM or direct-replacement parts.
3 Thermocouple & Electrode Replacement
The igniter electrode creates the spark that lights the burner, and it collects carbon deposits from combustion over time. A worn or fouled electrode either misfires or arcs to the wrong surface. Thermocouples (standing pilot models) fail from heat cycling. We clean, gap, and replace these components as needed and test ignition sequence before declaring the repair complete.
4 Propane Supply Diagnosis
A furnace that won't ignite despite good spark is often a propane supply problem — not a furnace problem. Causes include a failed two-stage regulator (very common on rigs 5+ years old), a nearly-empty tank that has insufficient vapor pressure in cold weather, a kinked or partially closed supply line, and solenoid valve failure. We test supply pressure at the furnace inlet to confirm before condemning the appliance itself.
5 Combustion Air & Exhaust Inspection
RV furnaces require unobstructed combustion air intake and exhaust ports — both typically accessed through vented panels on the exterior of the rig. Wasp nests and mud dauber nests are a common obstruction (especially on rigs in summer storage). A blocked exhaust causes the high-limit switch to trip, which shuts the furnace down as a safety measure. We inspect and clear both ports as part of every furnace call.
Frequently Asked Questions — RV Furnace Repair
Why won't my RV furnace ignite?
The most common causes are a faulty sail switch (a safety switch that confirms airflow before the burner fires), a failed igniter electrode, a bad circuit board, a failed thermocouple or limit switch, or insufficient propane pressure — including a regulator that's failed or a tank that's nearly empty. We diagnose the specific cause before recommending a repair.
My furnace fan runs but there's no heat. What's wrong?
If the blower runs but the burner never fires, the most likely causes are a failed sail switch, an ignition board fault, a bad electrode or igniter, or a propane supply problem. A furnace that blows air but doesn't ignite is telling you the safety system is working — something is preventing the gas valve from opening.
What RV furnace brands do you service?
We service Dometic (formerly Atwood) and Suburban RV furnaces — the two brands found in the vast majority of travel trailers, fifth wheels, and motorhomes on the road today. We carry common repair parts for both brands on the truck.
Can you repair my furnace at my campsite or storage lot?
Yes. We come to wherever your RV is parked — campground, storage facility, driveway, or roadside. Furnace repairs are among the most self-contained we do; the furnace compartment is typically accessible from outside the RV and most repairs require no shop equipment.
Is it safe to use a space heater while waiting for furnace repair?
A properly functioning electric space heater (1,500W plug-in type) is safe for short-term use on shore power. Do not use catalytic propane heaters or unvented combustion heaters inside an RV — they consume oxygen and produce carbon monoxide. If you're on shore power, a plug-in heater is a reasonable stopgap until we arrive.