When A Furnace Burner Won’t Stay Lit, Homeowners Face Cold Rooms, Higher Bills, And Potential Safety Concerns. This Article Explains The Most Common Causes, Step-By-Step Troubleshooting, Safety Precautions, And Repair Options So Readers Can Identify Whether A Simple DIY Fix Or Professional Service Is Needed.
| Symptom | Likely Cause | Quick Action |
|---|---|---|
| Pilot Light Or Burner Ignites Then Goes Out | Faulty Thermocouple Or Flame Sensor | Clean Or Replace Sensor; Check Pilot Flame |
| No Continuous Flame | Dirty Burner Or Clogged Orifice | Clean Burner Ports; Inspect Gas Supply |
| Clicking Then No Flame | Ignitor Or Electronic Ignition Fault | Test/Replace Ignitor; Check Ignition Module |
| Intermittent Operation | Thermostat, Gas Valve, Or Pressure Issue | Verify Thermostat Settings; Inspect Gas Valve |
Content Navigation
- How Furnaces Ignite And Why A Burner May Not Stay Lit
- Most Common Causes When A Furnace Burner Won’t Stay Lit
- Step-By-Step Troubleshooting When A Furnace Burner Won’t Stay Lit
- When To Call A Professional
- Typical Repair Options And Cost Estimates
- Preventive Maintenance To Keep A Burner Lit Reliably
- Safety Tips When A Furnace Burner Won’t Stay Lit
- Common Error Codes And What They Mean
- DIY Checklist For Homeowners
- Key Takeaways And Action Plan
- Useful Resources And References
How Furnaces Ignite And Why A Burner May Not Stay Lit
Understanding Furnace Ignition Basics Helps Troubleshoot When A Furnace Burner Won’t Stay Lit. Common Types Include Standing Pilot Systems And Electronic Ignition Systems Such As Hot Surface Ignitors Or Intermittent Pilot Ignition.
In Standing Pilot Systems, A Pilot Flame Is Constant And A Thermocouple Detects Heat To Keep The Gas Valve Open. In Electronic Systems, An Ignitor Lights The Main Burner And A Flame Sensor Confirms Combustion.
Most Common Causes When A Furnace Burner Won’t Stay Lit
Faulty Or Dirty Flame Sensor Or Thermocouple
A Flame Sensor Or Thermocouple Detects Flame Presence; If It’s Dirty Or Worn, It May Fail To Signal The Gas Valve, Causing The Burner To Shut Off Shortly After Ignition. Cleaning Or Replacing These Parts Often Fixes The Issue.
Pilot Light Problems
Pilot Flames That Are Too Small, Misaligned, Or Intermittent Can Fail To Keep A Thermocouple Hot Enough To Hold The Gas Valve Open. Debris, Drafts, Or A Weak Pilot Orifice Can Cause This.
Dirty Burners Or Obstructed Flame Ports
Soot, Dust, Or Insects Can Clog Burner Ports Or The Pilot Orifice, Producing A Weak Flame That Extiguishes. Regular Cleaning Is Required To Maintain A Stable Flame.
Faulty Ignitor Or Ignition Control
In Electronic Ignition Furnaces, A Cracked Hot Surface Ignitor Or A Failing Spark Module Can Ignite The Burner Briefly Or Not At All. The Ignition Module Must Detect Flame To Keep Gas Flowing.
Gas Supply Or Gas Valve Issues
Insufficient Gas Pressure, Partially Closed Shutoff Valves, Or A Malfunctioning Gas Valve Can Cause The Burner To Light Then Go Out. Utility Company Problems Or Internal Valve Failures Are Possible.
Flame Rollout, Pressure Switch, Or Venting Problems
Blocked Exhaust Vents, A Cracked Heat Exchanger, Or Negative Pressure Can Trigger Safety Switches Such As The Pressure Switch Or Flame Rollout Switch, Shutting Down The Burner To Prevent Danger.
Thermostat Or Control Board Faults
A Faulty Thermostat, Loose Wiring, Or A Control Board Error Can Interrupt The Ignition Or Flame Sensing Signals, Causing The Burner To Shut Down Unexpectedly.
Step-By-Step Troubleshooting When A Furnace Burner Won’t Stay Lit
Safety First
Turn Off Power To The Furnace And Shut Off The Gas At The Valve Before Inspecting Internal Components. If There Is Any Smell Of Gas, Evacuate The Home And Call The Gas Company Immediately.
Inspect The Pilot Flame Or Main Burner
For Standing Pilot Systems, Observe The Pilot Flame Size And Shape; It Should Wrap Around The Thermocouple. For Electronic Systems, Watch The Ignition Sequence And Note Any Error Codes On The Control Board.
Clean The Flame Sensor Or Thermocouple
Remove The Flame Sensor Or Thermocouple And Wipe Gently With Fine Grit Sandpaper Or An Emory Cloth To Remove Carbon Buildup. Reinstall And Test; Many Problems Resolve With Proper Cleaning.
Check And Clean Burners And Orifices
Inspect Burner Ports For Dirt, Rust, Or Spider Webs. Use A Soft Brush And Compressed Air To Clear Debris, Then Reassemble And Test For Proper Flame Stability.
Verify Gas Supply And Valve Operation
Ensure The Gas Shutoff Valve Is Fully Open And That Other Gas Appliances Operate Normally. If Low Pressure Or Supply Interruptions Are Suspected, Contact The Utility Or A Licensed Technician.
Test Ignitor And Control Components
Visually Inspect Hot Surface Ignitors For Cracks Or Breaks. Electronic Ignitors And Control Boards Require Multimeter Tests; Replace Faulty Components According To Manufacturer Specifications.
Check Venting, Pressure Switches, And Safety Devices
Inspect Exhaust Vents For Blockages From Birds, Snow, Or Debris. Verify The Pressure Switch Hoses Are Connected And Free Of Condensate; Replace Defective Safety Switches To Restore Proper Operation.
When To Call A Professional
Contact A Licensed HVAC Technician If Troubleshooting Requires Gas Valve Replacement, Heat Exchanger Inspection, Complex Electrical Diagnosis, Or If There Is A Persistent Gas Smell. Professionals Can Safely Perform Pressure Tests, Combustion Analysis, And Code-Compliant Repairs.
Typical Repair Options And Cost Estimates
Costs Vary By Region And Furnace Type. Typical Repairs Include Flame Sensor Cleaning Or Replacement ($75–$200), Ignitor Replacement ($150–$400), Gas Valve Replacement ($300–$900), And Burner Orifice Cleaning ($50–$150). Heat Exchanger Replacement Or Major Venting Work Is Significantly More Expensive.
Preventive Maintenance To Keep A Burner Lit Reliably
- Schedule Annual Professional Tune-Ups To Clean Burners, Inspect Heat Exchanger, And Test Safety Controls.
- Replace Filters Regularly To Maintain Proper Airflow And Combustion.
- Keep Vents And Terminals Clear Of Debris And Snow.
- Observe Pilot Flames During Routine Checks And Note Any Changes In Color Or Size.
Safety Tips When A Furnace Burner Won’t Stay Lit
Never Attempt Major Gas Or Electrical Repairs Without Turning Off Power And Gas. If Carbon Monoxide Detectors Trigger Or There Is Soot Or A Strong Odor, Evacuate And Seek Immediate Professional Assistance. Regular Maintenance And Prompt Attention To Irregular Flames Reduce Risk.
Common Error Codes And What They Mean
Many Modern Furnaces Display Flashing Lights Or Error Codes; Refer To The Manufacturer Manual To Interpret Codes. Frequent Codes Related To Burner Shutdown Include Flame Failure, Pressure Switch Open, And Ignition Lockout. Document Codes Before Calling A Technician.
DIY Checklist For Homeowners
- Turn Off Power And Gas Before Opening The Furnace Access Panel.
- Inspect Pilot Flame Or Watch Ignition Cycle For Errors.
- Clean Flame Sensor Or Thermocouple Carefully.
- Clear Burner Ports And Pilot Orifice Of Debris.
- Check Thermostat Batteries And Wiring Connections.
- Confirm Vents Are Clear Outside The Home.
- If Problem Persists, Gather Error Codes And Contact A Licensed HVAC Professional.
Key Takeaways And Action Plan
When A Furnace Burner Won’t Stay Lit, The Most Likely Causes Are Dirty Or Faulty Flame Sensors, Pilot Issues, Ignition Failures, Or Gas Supply Problems. Start With Visual Inspections And Safe Cleaning, Then Move To Component Testing Or Professional Help If Needed.
Document Observations, Any Error Codes, And The Sequence Of Events To Provide Clear Information To A Technician If Professional Service Is Required.
Useful Resources And References
Homeowners Seeking Additional Guidance Can Consult Manufacturer Manuals, Local Utility Safety Pages, And Certified HVAC Organizations Such As The Air Conditioning Contractors Of America For Technician Directories And Safety Recommendations.
Tips for Getting the Best HVAC Prices
- Prioritize Quality Over Cost
The most critical factor in any HVAC project is the quality of the installation. Don’t compromise on contractor expertise just to save money. - Check for Rebates
Always research current rebates and incentives — they can significantly reduce your overall cost. - Compare Multiple Quotes
Request at least three estimates before making your choice. You can click here to get three free quotes from local professionals. These quotes include available rebates and tax credits and automatically exclude unqualified contractors. - Negotiate Smartly
Once you've chosen a contractor, use the proven strategies from our guide — How Homeowners Can Negotiate with HVAC Dealers — to get the best possible final price.