Camper Furnace Not Working? Troubleshooting and Fixes for RV Heat Problems

When a camper furnace is not working, a cold night can turn stressful fast. This guide explains how RV propane furnaces operate, common failure points, and step-by-step troubleshooting. It covers quick checks, deeper diagnostics, safety tips, and brand-specific pointers for Suburban and Dometic/Atwood units. Use it to restore heat quickly and safely, whether boondocking or plugged into shore power.

How An RV Propane Furnace Works

Most U.S. campers use a forced-air propane furnace powered by 12-volt DC. Even on shore power, the furnace blower and control board still rely on the RV battery and converter. If battery voltage is low, the system may not light or will short-cycle.

When heat is called, the blower starts to purge the firebox. A sail switch confirms adequate airflow. The control board then opens the gas valve and fires the igniter. A flame sensor proves flame. If flame is unstable or not detected, the board shuts gas, retries, and eventually locks out.

A high-limit switch protects against overheating caused by blocked ducts or poor return airflow. The furnace pushes hot air through supply ducts and vents exhaust outside through a sealed combustion chamber, keeping indoor air separate from combustion gases.

Modern furnaces incorporate lockout logic. After several failed attempts, they may require a reset by turning the thermostat off and back on, or removing 12V power for a minute. Knowing this behavior can save time while troubleshooting.

Quick Safety Checklist Before You Start

Propane and combustion require caution. Before diving into a “camper furnace not working” diagnosis, review safety basics.

• Sniff test: If a raw propane smell is present, shut off the LP tank and ventilate. Do not ignite anything. Investigate leaks before proceeding.
• CO safety: Confirm your carbon monoxide detector is present and working. Replace batteries if needed.
• Fire safety: Have a class ABC fire extinguisher within reach. Keep combustibles away from furnace vents.
• Power awareness: Many checks require 12V power. Avoid short circuits and loose wire contact.
• Exhaust integrity: Ensure the exterior intake/exhaust is clear and intact. Do not operate with a damaged vent.

Fast Checks You Can Do In Minutes

These quick steps resolve many “RV furnace won’t ignite” complaints without tools.

• Thermostat: Set to Heat mode with a setpoint 5–10°F above room temperature. Replace batteries in wall thermostats if applicable.
• Battery voltage: Check at rest: 12.4–12.6V is healthy. Under blower load, avoid sag below ~11.0V. Low voltage causes lockouts.
• Fuses and breakers: Verify the 12V furnace fuse at the DC distribution panel. Reset any tripped breakers.
• Propane supply: Confirm the tank valve is open and not empty. Try the stove for a minute to purge air and verify gas flow.
• Regulator changeover: If using dual tanks with auto-changeover, ensure the selector is on a full tank.
• Vent check: Inspect the exterior intake/exhaust for insect nests, debris, or snow. Clear gently.
• Reset lockout: Turn the thermostat OFF for 30 seconds and back ON. If needed, pull the furnace fuse for 60 seconds to reset the board.

Diagnosing Common Symptoms

Nothing Happens When Calling For Heat

If the blower does not start, suspect a dead thermostat circuit, blown fuse, low battery, or a failed control board. Verify 12V at the furnace, confirm the thermostat is commanding heat, and inspect wiring connectors for corrosion or loose spades.

Blower Runs, But No Ignition

This usually points to an airflow interlock (sail switch not closing), empty propane, low regulator pressure, dirty igniter, blocked burner, or a bad gas valve. Listen for the click of the gas valve and the ticking igniter. Lack of clicking suggests ignition circuit issues.

Ignites, Then Shuts Down Quickly

If the flame lights but goes out within seconds, the flame sensor may not prove flame. Clean the flame rod with a non-abrasive pad, check the spark gap, confirm a strong ground, and verify stable propane pressure. Altitude and wind can worsen marginal sensing.

Short-Cycling Or Overheating

Furnace starts, heats briefly, then the limit switch trips from high temperature. Common causes include blocked supply ducts, restricted return air, crushed flex ducts, closed registers, or a dirty blower wheel. Restore airflow and inspect for pet hair buildup.

Fan Runs Forever, Heat Is Lukewarm

Insufficient combustion or a partially blocked burner can deliver weak heat. Also check for ducts disconnected behind cabinets, allowing hot air to dump into voids. Verify proper duct area per furnace specifications and correct any kinks.

Clicking Or Rattling Noises

Ticking is normal during ignition, but persistent metallic scraping suggests a failing blower motor or debris in the wheel. Shut down and inspect the blower assembly. Imbalance can trip the sail switch and reduce heat output.

Propane Smell Or Soot At The Exhaust

Raw gas smell indicates a leak or repeated failed ignition. Heavy soot at the exhaust hints at improper combustion. Stop operating and address leaks or have a professional check combustion and regulator pressure.

Quick Reference: Symptoms, Likely Causes, And Fixes

Battery And Power: The Hidden Culprit

Camper furnaces depend on solid 12V power. Weak batteries or corroded connections cause low blower speed, preventing the sail switch from closing and stopping ignition. Always measure voltage at the furnace under load, not just at the battery posts.

Healthy systems hold above ~11.0V while the blower starts. If voltage dives, charge the battery, fix bad grounds, or replace failing batteries. Confirm the converter provides ~13.4–13.8V on shore power and 14.2–14.6V during boost, depending on model.

Loose grounds are common. Clean and tighten chassis grounds near the furnace and battery. Inspect inline blade fuses at the furnace and the DC panel. Replace any heat-discolored connectors.

• Tools: Digital multimeter, wire brush, dielectric grease.
• Targets: Battery at rest 12.4–12.6V; under load >11.0V; converter output ~13.6V.

Propane Supply And Regulator Issues

A two-stage regulator should deliver ~11 inches water column (in. w.c.) under load. Low pressure leads to weak or no flame. High pressure risks sooting and unsafe combustion. Regulators wear out and can freeze in cold, damp conditions.

If the stove flame looks lazy or small, propane delivery may be compromised. Try switching tanks, warming a cold regulator with ambient heat (never open flame), or replacing an old regulator. Ensure pigtails and POL/ACME connections are tight and undamaged.

After tank changes, lines can be air-bound. Run a stove burner for 30–60 seconds to purge air, then retry the furnace. If problems persist, a manometer test at an appliance test port verifies pressure.

• Cold weather tip: Keep tanks above freezing with insulated covers and avoid overfilling.
• Leak check: Use a bubble solution on fittings; never a lighter.

Airflow, Ducting, And Return Air

Insufficient airflow is a top cause of “camper furnace not working right.” The sail switch and high-limit switch both depend on proper air movement. Blocked returns or crushed ducts cause overheating and lockouts.

Keep return air grilles open and clear of bedding, pet hair, and storage. Behind cabinets, check for kinked or disconnected flexible ducts. Open all registers during troubleshooting to maximize airflow and prevent nuisance trips.

Manufacturers specify minimum duct area. As a rule of thumb, mid-size furnaces need multiple open ducts totaling significant area. If a remodel reduced vents, restore adequate supply and return area per the furnace manual.

• Cleanliness: Vacuum lint, dust, and pet hair from returns and around the blower inlet.
• Duct integrity: Replace crushed or heat-damaged flexible ducts. Seal joints with foil HVAC tape, not cloth duct tape.

Sensors And Switches: Sail, Limit, And Flame

Sail switch: This airflow sensor must close before gas flows. Pet hair, dust, or weak blower speeds keep it open. Access the furnace compartment, gently clean the switch and ensure the blower wheel is clear. Replace if sticky or damaged.

High-limit switch: When exchanger temps exceed spec, the limit opens, shutting down the flame. If it trips repeatedly, find the airflow restriction. A persistently open limit may be failed and needs replacement with the correct temperature rating.

Flame sensor: Often integrated with the igniter. A thin oxide layer can interrupt flame rectification. Remove power, access the electrode, and lightly clean the rod. Confirm the ceramic is intact and the gap per manual (commonly around 1/8–3/16 inch).

Ignition System And Burner Health

The igniter must spark at the burner for clean lighting. Misaligned electrodes, cracked ceramic, or a weak board spark will cause misfires. Adjust the electrode position and verify strong, consistent spark during the ignition window.

Burner and orifice blockages from rust flakes or insects (mud daubers, spiders) are common. Do not ream orifices with wire; use compressed air to clear. Inspect the burner for corrosion and proper flame shape: steady blue with minimal yellow tipping indicates good combustion.

Control Boards And Flash Codes

Suburban and Dometic/Atwood furnaces typically include an LED that blinks diagnostic codes. Count flashes after a failure to narrow the fault. Codes vary by model, but patterns commonly indicate ignition lockout, limit switch open, or flame sense failure.

Control boards can fail from moisture or vibration. Before replacing, rule out power, ground, airflow, and propane issues. If replacing a board, match the part number or use a reputable universal replacement designed for the furnace series.

Access to the board is usually from the furnace service side or through an exterior panel. Photograph wiring before removal. Maintain correct polarity and secure all grounds for reliable sensing.

Thermostats And Control Signals

Most RV furnaces use a simple 2-wire thermostat that closes a circuit to call for heat. Analog thermostats can drift; digital replacements improve accuracy and may reduce short-cycling. Ensure thermostat wiring is intact and not shorted to the metal wall.

Combo HVAC controls (such as Dometic multi-zone) may route furnace calls through a control module. If the air conditioner and fan work but heat does not, check the furnace call wiring at the module and verify the furnace mode is enabled.

Cold Weather And High Altitude Considerations

At altitude, thinner air reduces oxygen to the burner, making ignition and flame sensing harder. Some furnaces derate above ~5,000–7,000 feet. Expect longer ignition times and more sensitivity to airflow and voltage issues.

Extreme cold thickens oil in blower bearings and can freeze regulators. Keep batteries warm and fully charged, use tank covers, and protect exterior vents from wind-driven snow without blocking intake/exhaust.

• Skirting and sealing: Reduce drafts around the undercarriage to lower furnace load.
• Duct to bays: Some rigs route heat to water bays to prevent freezing. Confirm those ducts are intact.

Maintenance Schedule To Prevent Future No-Heat Events

• Every trip: Test the furnace before departure. Verify CO/LP detectors.
• Quarterly: Vacuum return grilles; clear exterior vents; check duct registers.
• Biannually: Inspect and clean burner area, electrode, and flame sensor; tighten grounds and connectors.
• Annually: Pressure test propane system; verify regulator output (11 in. w.c. under load); replace furnace filter screens if equipped.
• Every 5–7 years: Consider regulator replacement; evaluate blower motor bearings if noisy.
• After storage: Purge air from propane lines via the stove, then test furnace operation.

When To Call A Professional

DIY fixes address many “camper furnace not working” cases, but some issues need certified service, especially gas leaks, recurring sooting, cracked heat exchangers, or persistent lockouts after basic checks. Safety and warranty concerns make expert help wise.

• Expected costs: Diagnostic visit $100–$200; common parts like sail switch or limit switch $20–$60; control board $120–$250; blower motor $150–$300; regulator $40–$90. Prices vary by region.
• Documentation: Bring model and serial numbers, symptom notes, and any flash codes to speed repair.

DIY Tools And Spare Parts Checklist

• Tools: Multimeter, nut drivers, Torx/Phillips drivers, flashlight, compressed air, non-abrasive pad, leak-detect solution, foil HVAC tape.
• Consumables: Dielectric grease, cable ties, replacement fuses, spare thermostat batteries.
• Spare parts: Sail switch, limit switch, igniter/flame rod, exterior vent screen, short flex duct section, universal control board (if traveling remote).

Brand-Specific Pointers

Suburban SF Series: Common in travel trailers and fifth-wheels. Maintain clear return air and adequate supply duct area per the Suburban manual. LED codes often appear on or near the control board. Use OEM-rated limit switches and electrodes.

Dometic/Atwood 85XX/89XX: Known for sail switch sensitivity to dust. Ensure correct electrode gap and clean ground connections. Some models have outside access for service; others require interior panel removal. Verify duct sizes meet manual specs.

Truma VarioHeat/Combi: These are sealed, high-efficiency units with brand-specific diagnostics. User service is limited. For persistent faults or error codes, contact an authorized Truma service partner for safe, warranty-compliant repairs.

Step-By-Step Diagnostic Walkthrough

Use this ordered approach to efficiently isolate the fault and avoid parts-chasing. It addresses the majority of “RV furnace won’t start” scenarios.

1. Verify demand: Thermostat on Heat, setpoint above room temp, fan Auto.
2. Confirm power: Measure 12V at the furnace with blower running; repair low voltage or grounds.
3. Check airflow: Open all registers, clear returns, inspect ducts. Clean blower intake and sail switch.
4. Propane flow: Confirm tank level, regulator position, stove flame quality. Purge lines, inspect for leaks.
5. Ignition: Listen for spark and gas valve click. If no spark, inspect igniter and board. If spark but no light, clean burner and electrode, verify pressure.
6. Flame sense: Clean flame rod, improve ground, correct spark gap. Observe flame stability.
7. Overheat trips: If shutting down after heating, test/replace limit switch and restore airflow.
8. Reset and retest: Power-cycle to clear lockout; recheck operation through multiple cycles.

Useful Specifications And Reference Resources

Always cross-check with the furnace’s installation and service manual for model-specific specs, minimum duct area, and sensor part numbers. Manufacturer guidelines ensure safe operation and efficient heating.

• Suburban Furnace Manuals (Airxcel)
• Dometic/Atwood Service Resources
• Truma Heating Technical Info
• RV Industry Association Safety Resources

What To Do If Heat Still Won’t Stay On

If the camper furnace still is not working after completing the checklist, capture details before seeking service. Note ambient temperature, altitude, battery voltage during start, flame behavior, and any LED flash codes. This context helps pinpoint elusive faults.

Meanwhile, use safe supplemental heat like electric space heaters only when on shore power, keeping clearances and electrical limits in mind. Avoid unvented propane heaters inside RVs due to CO and moisture risks.

Key Takeaways For Faster Heat Recoveries

• Power first: Most no-heat calls trace to low 12V voltage or bad grounds.
• Air matters: Airflow trips shut furnaces down; keep returns and ducts clear.
• Clean ignition: Spark gap, flame rod cleanliness, and burner health drive reliable lighting.
• Propane stability: Healthy regulators and purged lines prevent misfires and sooting.
• Reset smartly: Clear lockouts after fixing the cause, not before.

With these methods, many “camper furnace not working” issues can be resolved quickly and safely, restoring dependable heat for the road ahead.