Gas Furnace Pilot Light Out: Causes, Troubleshooting, and Repair

The pilot light going out on a gas furnace is a common winter disruption that can leave a home cold and raise safety concerns. This article explains why a gas furnace pilot light out condition occurs, outlines safe troubleshooting steps, and describes repairs and preventive maintenance. The goal is to help homeowners decide when a DIY fix is appropriate and when to call a licensed HVAC professional.

Symptom	Quick Check	Possible Fix
Pilot Light Out	Attempt to relight following instructions	Relight pilot; replace thermocouple if repeats
Burner Won’t Stay Lit	Observe flame shape and color	Clean or replace thermocouple, check gas valve
Smell Of Gas	Evacuate and call gas company	Do not relight; professional inspection

How A Pilot Light Works

A pilot light is a small, continuously burning flame that ignites the main burners when the thermostat calls for heat. Traditional standing pilots are common in older gas furnaces. Modern systems often use electronic ignition, which eliminates a continuous pilot flame but can fail in similar ways. Understanding the pilot’s role helps diagnose why the gas furnace pilot light out problem occurs and what components are involved.

Common Causes Of A Pilot Light Going Out

Pilot Flame Shape And Draft

A weak or distorted flame is more likely to be extinguished. Drafts from open windows, attic fans, or negative pressure in tight homes can blow out the pilot. Check for drafts and vents that might affect the furnace room.

Dirty Pilot Orifice

Dirt, soot, or spider webs can clog the pilot orifice and reduce gas flow to the pilot. A restricted orifice produces a small, unstable flame that often goes out.

Faulty Thermocouple Or Thermopile

The thermocouple detects the pilot flame and signals the gas valve to stay open. A failing thermocouple or thermopile will not register heat properly, causing the gas valve to close and the pilot to go out. This is one of the most common mechanical causes.

Gas Supply Or Gas Valve Problems

Low gas pressure from the utility, closed or partially closed shutoff valves, or a defective gas control valve can prevent adequate gas from reaching the pilot. If multiple appliances are affected, it could be a supply issue.

Faulty Pilot Assembly Or Igniter

Corrosion, physical damage, or loose connections in the pilot assembly or electronic igniter can disrupt ignition. Modern electronic ignition modules and control boards can also fail and stop pilot or spark generation.

Safety First: What To Do If The Pilot Light Is Out

If the homeowner smells gas, evacuate immediately, avoid switching electrical devices or open flames, and call the gas utility or 911 from a safe location. Do not attempt to relight the pilot until a professional confirms it is safe.

Before relighting, shut off the gas and wait several minutes for residual gas to dissipate if a strong odor is present. Turn off the furnace switch and the gas supply valve at the appliance. Safety is the priority when dealing with gas appliances.

How To Relight A Pilot Light Safely

Follow the furnace manufacturer’s instructions found on the furnace door or owner’s manual. The general steps below apply to many standing pilot systems but may not fit all models or electronic ignition systems.

1. Turn the thermostat to OFF and the furnace switch to OFF. Find the gas control knob and set it to OFF.
2. Wait five minutes for any residual gas to clear if a gas odor was present.
3. Turn the gas control knob to PILOT, depress the knob (or pilot button), and hold it while using an approved long-reach lighter or the furnace’s built-in igniter to light the pilot.
4. Hold the gas control depressed for 30–60 seconds after lighting to heat the thermocouple, then release. If the pilot stays lit, set the gas control to ON and restore power.
5. If the pilot won’t stay lit after several tries, stop and proceed to troubleshooting components or call a professional.

Troubleshooting Steps Before Calling A Technician

These diagnostic checks can identify common causes of a gas furnace pilot light out issue and help determine if a simple repair will resolve it.

Check For Drafts And Ventilation Issues

Inspect nearby windows, doors, exhaust fans, or dryer vents that could reverse pressure and blow out the pilot. Ensure the furnace door is properly closed to maintain correct airflow and combustion chamber pressure.

Inspect The Pilot Flame

A healthy pilot flame is steady and mostly blue with a small inner cone. A yellow, flickering, or sputtering flame indicates contamination or improper gas-air mixture. Cleaning or service is likely required.

Clean The Pilot Orifice

With the gas off and the furnace cool, remove the pilot assembly (if accessible) and clean the orifice gently with compressed air or a thin wire designed for orifices. Avoid enlarging the orifice and follow manufacturer guidance.

Test Or Replace The Thermocouple

Thermocouples are inexpensive and commonly replaced. Measure millivolts with a multimeter while the pilot is lit; a weak reading indicates failure. Replacement requires basic mechanical skills, but homeowners uncomfortable with gas appliances should call a pro.

Check Gas Supply And Shutoff Valves

Confirm the furnace gas valve is fully open and other household gas appliances have normal operation. If gas supply is suspected, contact the gas utility.

When To Call A Professional HVAC Technician

Immediate professional service is recommended if any of the following occur: persistent pilot outages after relighting, smell of gas, malfunctioning gas valve, repeated thermocouple failures, or if the furnace uses sealed combustion where access is limited.

A qualified technician can safely test gas pressure, inspect control boards, replace defective components, and verify combustion safety. Licensed professionals also ensure compliance with local codes and manufacturer warranty requirements.

Costs And Typical Repairs

Repair costs vary by region and furnace type. Typical out-of-pocket repairs for a pilot light issue may include a thermocouple replacement ($75–$200 installed), pilot assembly cleaning or repair ($50–$150), or gas valve replacement ($300–$1,000+). Diagnostics or service calls often add $75–$150.

Electronic ignition system repairs can be more costly but offer energy savings by eliminating a continuous pilot flame. Consider long-term savings when comparing repair vs. retrofit to electronic ignition.

Preventive Maintenance To Avoid Pilot Light Problems

Regular maintenance reduces the risk of a gas furnace pilot light out scenario. Annual professional tune-ups should include inspection and cleaning of the pilot or ignition system, combustion analysis, gas pressure check, and thermostat calibration.

Homeowners can help by keeping the furnace area clean, sealing drafts, replacing air filters regularly, and following manufacturer recommendations for service intervals.

Upgrading From Standing Pilot To Electronic Ignition

Converting to an electronic ignition system eliminates a continuously burning pilot, improving safety and reducing fuel consumption. The retrofit cost depends on furnace model and labor, but typical payback from fuel savings can occur over several heating seasons.

Pros of conversion include more reliable ignition, reduced pilot-related outages, and improved efficiency. Consult a licensed HVAC technician for compatibility and cost estimates.

Common FAQs About Pilot Light Problems

Why Does The Pilot Light Keep Going Out?

Frequent outages often point to a failing thermocouple, dirty pilot orifice, drafts, or a malfunctioning gas valve. Professional diagnosis is recommended if relighting fails repeatedly.

Is It Dangerous If The Pilot Light Goes Out?

A single pilot outage is not inherently dangerous if handled properly, but a strong gas smell or repeated failures requires immediate professional attention. Always prioritize safety and avoid relighting if gas odor is present.

Can A Homeowner Replace A Thermocouple?

A mechanically and safety-aware homeowner can replace a thermocouple if comfortable working with gas appliances and following manufacturer instructions. If unsure, hire a licensed technician.

How Often Should A Furnace Pilot Be Serviced?

Annual inspection and cleaning during scheduled maintenance helps prevent pilot outages and ensures safe operation. More frequent checks may be needed for older equipment or houses with combustion air issues.

Resources And Next Steps

For step-by-step relighting instructions specific to the furnace model, consult the owner’s manual or the label on the furnace access panel. For gas smells or complex issues, contact the local gas utility or a licensed HVAC professional. Professional service ensures proper testing, safe repairs, and compliance with local codes.

When facing a gas furnace pilot light out situation, prioritize safety, try basic diagnostic checks if comfortable, and call a qualified technician for persistent or hazardous conditions.