Rv Furnace Starts Then Shuts Off: Causes and Fixes

The RV furnace starting then shutting off can be frustrating and potentially unsafe. This article outlines the most common causes, diagnostic steps, practical fixes, and preventive maintenance for RV furnaces so owners can restore reliable heat quickly. Focus is on actionable troubleshooting for propane and electric ignition systems used in U.S. recreational vehicles.

Symptom	Likely Cause	Quick Fix
Furnace lights then dies	Faulty flame sensor or draft switch	Clean sensor, check wiring
Blower stops shortly after start	Limit switch or thermostat problem	Test thermostat, inspect limit switch
Igniter sparks but no flame	No propane or blocked orifice	Check propane supply, clean orifice

How RV Furnaces Operate

Understanding basic furnace operation helps diagnose why an RV furnace starts then shuts off. Most RV furnaces use a forced-air burner with a thermostat, control board, blower motor, limit/draft switch, flame sensor or thermocouple, and safety switches. When the thermostat calls for heat, the control board powers the blower and opens the gas valve while the ignition system lights the burner. If the flame sensor does not confirm combustion or a safety switch detects an unsafe condition, the system shuts the unit down.

Common Causes For An RV Furnace Starting Then Shutting Off

Poor Flame Detection

A frequent cause is a dirty or failing flame sensor or thermocouple. If the control board can’t sense flame presence, it will cut gas to prevent unsafe conditions. Symptoms include a consistent short run time before shutdown and visible flame then shutdown.

Blocked Or Dirty Burner Or Orifice

Soot, spider webs, or debris can block the burner orifice or air intake, causing intermittent flame or poor combustion. This leads the furnace to start then shut off as the flame becomes unstable.

Propane Supply Problems

Low tank pressure, an empty tank, or a malfunctioning regulator causes the furnace to lose fuel after initial ignition. Tanks with automatic changeover valves or inline filters can also restrict flow and cause shutdowns.

Faulty Draft Or Limit Switch

Draft or limit switches protect against overheating or unsafe drafts. A failing draft switch may misread airflow and shut the furnace off when it’s actually operating normally. Intermittent contact or vacuum hose issues can cause immediate shutdown.

Thermostat Or Control Board Issues

If the thermostat sends sporadic signals or the control board has faulty relays, the system may power down unexpectedly. Electronic control problems often show irregular behavior not linked to mechanical faults.

Blower Motor And Capacitor Failures

A blower motor that stalls or a failing capacitor will cause the furnace to shut down to prevent overheating. This may happen shortly after start as the motor draws higher current when warm.

Diagnostic Steps To Identify The Problem

Systematic diagnosis isolates the root cause safely and efficiently. Use these ordered steps to avoid unnecessary parts replacement.

1. Check Propane Supply: Verify tank level and regulator operation. Swap tanks or test with a known-good supply if possible.
2. Observe Startup Sequence: Note whether the ignitor clicks, burner lights, then goes out, or if the ignitor runs without ignition.
3. Inspect Flame Sensor/Thermocouple: Clean lightly with fine emery cloth and ensure proper alignment to flame.
4. Check For Error Codes: Many RV furnaces flash LED codes on the control board; reference the manufacturer’s code chart.
5. Test Draft/Limit Switch: Gently tap or listen for switch operation; inspect vacuum lines for cracks or disconnections.
6. Measure Voltage: Confirm correct voltage to blower motor and control board using a multimeter; low voltage can indicate wiring or converter issues.
7. Examine Venting And Burner: Remove access cover and inspect burner tube, orifice, and combustion chamber for debris or nests.

Step-By-Step Fixes

Clean Or Replace Flame Sensor

Turn off power and propane before servicing. Remove the flame sensor and gently clean with fine abrasive or alcohol. If cleaning does not help or sensor shows corrosion, replace it. Tip: Ensure replacement part matches the furnace model.

Clear Burner, Orifice, And Venting

Remove the burner assembly and clean with compressed air, a soft brush, or pick out obstructions. Use caution around orifices; do not enlarge holes. Check the exterior vent for nests and clear as needed.

Check And Restore Propane Supply

Confirm the tank has sufficient propane and the valve and regulator are functioning. Replace inline filters if present. If an automatic changeover regulator is frozen or failing, temporarily bypass or replace it per manufacturer guidance.

Inspect And Replace Draft/Limit Switch Or Vacuum Hose

Locate the draft or limit switch and vacuum hose to the intake. Replace cracked hoses and test switch continuity with a multimeter. If the switch fails to hold during operation, replace it.

Test And Replace Blower Motor Or Capacitor

If the blower stalls, check for obstructions and test the motor capacitor. Replace a weak capacitor and ensure motor bearings are free. Safety: Discharge capacitors before handling.

Repair Or Reset Thermostat And Control Board

Replace batteries in thermostats and ensure proper wiring. If the control board shows error codes or damaged components, consider replacing the board or consulting manufacturer support. Firmware resets can sometimes clear glitches; follow the manual.

Maintenance Practices To Prevent Recurrence

Regular maintenance reduces the chance an RV furnace starts then shuts off unexpectedly. Perform these tasks seasonally and before winter use.

• Clean burner assembly, orifice, and vent openings annually.
• Inspect and replace the flame sensor or thermocouple as needed.
• Check propane tank levels, regulator condition, and hoses monthly during travel season.
• Test blower motor and capacitor yearly and keep moving parts lubricated if specified by manufacturer.
• Run furnace briefly during warm months to identify issues before cold weather.

Safety Considerations

Working on an RV furnace involves propane, electricity, and combustion components. Always shut off propane and disconnect 12V power before opening the access panel. Ensure proper ventilation when testing and never bypass safety switches. If there is a strong gas odor or suspected CO leak, evacuate and contact emergency services.

When To Call A Professional

Some problems require a certified RV technician or HVAC pro. Seek professional help if troubleshooting does not resolve the issue, if control board replacement is needed, or if there are persistent propane leaks, strong odors, or suspected carbon monoxide issues. Certified techs have the tools to test gas pressure, verify electrical integrity, and handle sealed combustion systems.

Common Manufacturer Differences And Replacement Part Tips

Popular RV furnace brands include Suburban, Atwood (now Dometic brand variants), and Truma. Each makes slightly different flame sensors, orifices, and control boards. Use the furnace model number when ordering parts and avoid generic components unless specified. Match orifice size to the fuel type (LP vs. NG) and verify part compatibility with the serial/model label inside the furnace access panel.

Costs And Time Estimates

Simple maintenance tasks like cleaning a flame sensor or clearing a vent often take 30–60 minutes and cost little. Parts such as flame sensors, orifices, or limit switches typically range from $20–$100. Control boards or blower motors may cost $150–$400 and require a technician for safe installation. Labor costs vary across regions but expect higher rates for emergency mobile service.

Frequently Asked Questions

Why Does The Furnace Light Then Shut Off After A Few Seconds?

This usually indicates flame detection failure, draft switch activation, or insufficient propane pressure. Cleaning the sensor, checking vacuum hoses, and verifying propane supply are first troubleshooting steps.

Can Low Battery Or Weak Converter Cause The Furnace To Shut Off?

Yes. The furnace needs stable 12V DC power to run blowers and control circuits. Low battery voltage or a weak converter can cause the system to behave erratically and shut down.

Is It Safe To Run The Furnace With A Partial Blockage?

No. Blocked combustion air or exhaust can lead to incomplete combustion and carbon monoxide buildup. Clear venting and combustion areas before operating the furnace.

How Often Should The Burner Or Flame Sensor Be Replaced?

There’s no fixed interval, but inspect them annually. If cleaning does not restore consistent operation, replacement is advised to prevent repeated shutdowns.

Additional Resources

Owners should consult the furnace manual for model-specific troubleshooting and error code charts. Manufacturer websites and certified RV service centers provide diagrams and replacement part numbers. For safety-related questions about propane or carbon monoxide, refer to the U.S. Consumer Product Safety Commission and National Fire Protection Association resources.

Key Takeaway: An RV furnace that starts then shuts off is commonly caused by flame detection issues, propane supply interruptions, blocked components, or failing safety switches. Systematic diagnostics—check propane, clean sensors and burners, inspect switches and wiring—resolves most problems; consult a pro for gas leaks, control board failures, or persistent faults.