Furnace Pilot Lights Go Out: Common Causes & How to Fix Them
Why Do Furnace Pilot Light Issues Occur?
A furnace pilot light is a small, continuously burning flame that ignites the burners when your heating system kicks on. When the pilot light goes out, your furnace may fail to heat your home, leaving you in the cold. Understanding the reasons behind furnace pilot light issues can help prevent frequent outages and ensure your system operates efficiently.
Common Causes of a Furnace Pilot Light Going Out
- Drafts or Airflow Disruptions
Strong drafts from windows, vents, or open doors can blow out the pilot light. If this happens frequently, check for nearby sources of air movement. Weatherstripping or sealing gaps around doors and windows can help prevent drafts from affecting the pilot light. - Dirty or Clogged Pilot Orifice
Over time, dust and debris can accumulate in the pilot light’s orifice, restricting the gas flow and causing the flame to weaken or go out completely. Regular cleaning and maintenance can help keep the orifice clear, ensuring a steady flame. - Faulty Thermocouple
The thermocouple is a safety sensor that detects the pilot light’s flame. If it malfunctions or is misaligned, it may incorrectly shut off the gas supply, extinguishing the pilot light. A worn-out thermocouple should be replaced to maintain proper furnace function. - Gas Supply Issues
If your furnace isn’t getting enough gas due to a closed valve, a damaged gas line, or a supply issue from the provider, the pilot light may not stay lit. Check to ensure the gas valve is fully open and your home’s gas supply is functioning properly. If gas issues persist, contacting a professional is recommended. - Moisture Buildup or Condensation
Excess moisture inside the furnace can interfere with the pilot light’s ability to stay ignited. This is common in humid environments or if there’s a leak in your system. Ensuring proper ventilation and checking for leaks can help mitigate this issue.
How to Fix a Furnace Pilot Light That Keeps Going Out
- Turn Off the Furnace
Before performing any maintenance, turn off the gas and power to your furnace to ensure safety. - Inspect for Drafts
Identify and eliminate potential sources of strong airflow around your furnace. This may include closing nearby windows, adjusting vents, or sealing gaps. - Clean the Pilot Orifice
Use compressed air or a thin wire to remove any dust or debris from the pilot opening. Keeping the area around the pilot light clean can prevent future clogging. - Check the Thermocouple
If the thermocouple is misaligned, gently adjust it so the tip is in the direct path of the pilot flame. If it’s faulty, replacing it may be necessary. Testing the thermocouple’s responsiveness using a multimeter can help determine if it’s working correctly. - Ensure the Gas Valve Is Open
Verify that the gas valve is fully open and that your home’s gas supply is not interrupted. If you suspect an issue with the gas line, consult a professional for further inspection. - Relight the Pilot Light
Follow your furnace manufacturer’s instructions to safely relight the pilot light. This typically involves holding down the reset button while igniting the flame. If the flame does not stay lit, there may be an issue with the thermocouple or gas supply that needs professional attention.
Signs You May Need Professional Help
While many furnace pilot light issues can be resolved with simple troubleshooting, some situations may require professional assistance. Here are some signs that indicate a more serious problem:
- Repeated Pilot Light Failures: If the pilot light keeps going out despite relighting efforts, there may be an underlying issue with the gas supply, thermocouple, or burner assembly.
- Yellow or Flickering Flame: A properly functioning pilot light should burn a steady blue flame. A yellow or flickering flame may indicate incomplete combustion, which could be caused by dirty burners or poor ventilation.

- Strange Odors or Gas Smell: If you detect a strong gas smell around your furnace, turn off the gas supply immediately and contact a professional for a thorough inspection.
- Unusual Noises from the Furnace: Hissing, popping, or rumbling noises may indicate issues with the burner, heat exchanger, or pilot assembly, all of which require expert evaluation.
Preventing Future Pilot Light Issues
To keep your furnace running smoothly and avoid unexpected pilot light failures, consider these preventative measures:
- Schedule Regular Maintenance: Annual inspections by a professional HVAC technician can help identify and address potential issues before they escalate.
- Keep the Pilot Light Area Clean: Dust and debris buildup can interfere with the pilot light’s performance. Cleaning the surrounding area regularly can help maintain a steady flame.
- Check for Drafts and Airflow Disruptions: Ensure your furnace is positioned away from windows, doors, and other sources of strong airflow.
- Test Your Thermocouple Periodically: A malfunctioning thermocouple is a common cause of pilot light failures. Testing and replacing it as needed can prevent disruptions in your heating system.
- Monitor Gas Supply and Pressure: Low gas pressure or supply interruptions can impact the pilot light’s stability. Keeping an eye on these factors can help prevent unexpected outages.
Understanding Your Furnace’s Ignition System
Modern furnaces may use different ignition systems to light the burners, and not all models rely on a traditional pilot light. Understanding how your furnace operates can help you troubleshoot issues more effectively:
- Standing Pilot Light: Found in older furnaces, this system requires a continuously burning flame to ignite the burners.
- Intermittent Pilot Light: Newer models use an electronic ignition system that lights the pilot only when needed.
- Hot Surface Ignition: This system uses a heating element to ignite the burners without the need for a traditional pilot light.

If your furnace has an electronic ignition system and is experiencing issues, troubleshooting steps may differ from those for a standing pilot light system.
Conclusion
Furnace pilot light issues can be frustrating, especially during cold winter months when reliable heating is essential. By understanding the common causes of pilot light failures and taking the necessary troubleshooting steps, homeowners can keep their furnaces running efficiently. However, if problems persist, seeking professional assistance is always the best course of action to ensure safety and comfort in your home.
Contact us for more information or to request an appointment with our furnace experts.
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