Pilot Light Keeps Going Out on Furnace: Causes, Fixes, and Safety Tips

The pilot light on a furnace that keeps going out is a common issue for homeowners and renters. This article explains why the pilot light keeps going out on furnace systems, how to diagnose the problem, step-by-step repair and maintenance guidance, safety precautions, and when to call a professional. Understanding these factors can help restore reliable heating and reduce repair costs.

Symptom	Likely Cause	DIY Fix	When To Call A Pro
Pilot Keeps Going Out After Lighting	Faulty Thermocouple Or Pilot Orifice	Clean Pilot, Replace Thermocouple	If Replacement Or Gas Line Work Required
Pilot Flickers Or Weak Flame	Clogged Orifice, Low Gas Pressure	Clean Orifice, Check Gas Valve	Persistent Low Pressure
Pilot Out During Wind Or Drafts	Ventilation Or Draft Issue	Seal Drafts, Redirect Venting	Chimney/Vent Repair
Pilot Light Goes Out Randomly	Gas Control Valve/Flame Sensing Problems	Inspect Wiring, Replace Valve	Complex Controls Or Recurrent Failures

How A Furnace Pilot Light Works

The pilot light is a small, continuously burning flame that ignites the main burners when the thermostat calls for heat. In older furnaces a standing pilot uses a thermocouple or thermopile to sense the flame and keep the gas valve open. Modern systems may use electronic ignition, but many homes still rely on standing pilot assemblies.

When the pilot light keeps going out on furnace systems, the control circuit that senses the flame fails to register a flame or the flame itself is disrupted. Identifying whether the problem is mechanical, electrical, or environmental is the first diagnostic step.

Common Causes Why Pilot Keeps Going Out On Furnace

1. Faulty Thermocouple Or Thermopile

The thermocouple is a safety sensor positioned in the pilot flame. If it’s dirty, bent, or worn out, it won’t produce the required millivoltage to hold the gas valve open, causing the pilot to shut off. Thermocouples degrade over time and are a frequent cause of pilot outages.

2. Clogged Pilot Orifice Or Dirt In Pilot Assembly

Debris, spider webs, or soot can block the pilot orifice or tube, reducing gas flow and weakening the flame. A weak or yellowish flame is often a sign of a clogged orifice. Cleaning the pilot assembly often restores consistent operation.

3. Drafts, Airflow, Or Venting Issues

Drafts from open windows, improperly sealed doors, or nearby vents can blow out the pilot flame. Chimney or vent obstructions can also alter airflow around the pilot. Addressing drafts and venting ensures the flame remains steady.

4. Faulty Gas Control Valve Or Pressure Problems

The gas control valve regulates gas flow to the pilot and main burners. Malfunctioning valves or low incoming gas pressure cause intermittent pilot outages. These issues may require professional diagnosis and repair due to gas safety considerations.

5. Corrosion, Loose Connections, Or Wiring Issues

Electrical connections to the gas valve, limit switches, or flame sensors can corrode or loosen, interrupting the safety circuit. Inspecting wiring and terminals helps identify intermittent failures that make the pilot go out.

6. Age And Wear Of Furnace Components

Older furnaces naturally develop worn parts: thermocouples lose sensitivity, pilot assemblies corrode, and gas valves wear out. When pilot outages are recurrent in an aging furnace, replacement may be the most cost-effective solution.

Diagnostic Checklist: How To Determine Why The Pilot Keeps Going Out

Safety first: always turn off gas and electricity to the furnace before inspecting or repairing. If unsure, call a qualified technician.

• Visual Inspection: Look for soot, corrosion, or a yellow/pulsing pilot flame.
• Check For Drafts: Observe whether doors, windows, or vents affect the flame.
• Test Thermocouple: Using a multimeter measure millivolt output while the pilot is lit; low output indicates replacement.
• Clean Pilot Orifice: Remove debris with compressed air or a thin wire designed for pilot cleaning.
• Inspect Gas Valve: Smell for gas leaks and listen for unusual valve noises; valve failure often requires a pro.
• Evaluate Recent Work: New construction, insulation, or vent changes can create draft issues affecting the pilot.

Step-By-Step DIY Fixes When Pilot Keeps Going Out On Furnace

1. Clean The Pilot Assembly

Turn off the gas and let components cool. Remove the pilot tube shield and gently clean the orifice with compressed air or a specialized pilot cleaning tool. Reassemble and relight per manufacturer instructions.

2. Replace The Thermocouple

Thermocouples are inexpensive and user-replaceable. Turn off gas, unscrew the thermocouple from the gas valve and pilot bracket, and fit the new unit. Ensure the tip sits directly in the pilot flame and tighten connections snugly, then test.

3. Check And Tighten Electrical Connections

Inspect wires to the gas valve, flame sensor, and thermostat. Tighten loose terminals and clean corroded contacts. Replace frayed wiring and retest the system.

4. Adjust Or Relocate The Pilot Flame Shield

If drafts are the issue, add or adjust the pilot shield or reposition the furnace if possible. Seal nearby air leaks that create cross-drafts to stabilize the flame.

5. Inspect Venting And Chimney

Ensure exhaust venting and chimneys are clear of birds’ nests, debris, or blockages that alter combustion air flow. If venting is blocked, do not operate the furnace until cleared due to carbon monoxide risk.

When DIY Is Not Enough: Professional Repairs And Replacements

Certain scenarios require licensed HVAC technicians: suspected gas leaks, failing gas control valves, persistent low gas pressure, or complex control board failures. Professionals have tools to measure gas pressure, test valve operation, and safely replace high-voltage or gas components.

If the furnace is old and pilot outages are recurring despite repairs, a professional should evaluate whether a conversion to electronic ignition or full furnace replacement is more economical and energy-efficient.

Safety Tips When The Pilot Keeps Going Out On Furnace

• Detect Gas Smell: If gas odor is present, leave the home immediately and call the gas utility or 911 from a safe location.
• Ventilation: Keep the area ventilated during inspection but avoid cross drafts that blow out the pilot.
• No Open Flames: Avoid using matches or lighters when a leak is suspected.
• Carbon Monoxide Safety: Install CO detectors and never operate a furnace with blocked vents or incomplete combustion.
• Follow Manufacturer Instructions: Use the furnace manual for lighting procedures and part specifications.

Preventive Maintenance To Stop The Pilot From Going Out

Regular maintenance reduces the chance that the pilot light keeps going out on furnace systems. Annual professional tune-ups include burner inspection, pilot cleaning, thermocouple testing, gas pressure checks, and safety control verification.

• Schedule yearly HVAC inspections before the heating season.
• Keep the area around the furnace clean and free of dust and debris.
• Seal drafts around doors and windows to prevent flame disturbance.
• Replace aging components proactively: thermocouples, pilot tubes, or gas valves as recommended.

Costs And Timeframes For Common Fixes

Repair	Typical DIY Time	Estimated Cost (USD)
Clean Pilot Orifice	15–30 Minutes	$0–$25 (tools)
Replace Thermocouple	30–60 Minutes	$15–$60
Gas Valve Replacement	1–2 Hours (Pro)	$200–$600
Professional Inspection/Tune-Up	1–2 Hours	$80–$200

Prices vary by region and furnace model. For gas valve work or complex diagnostics, hiring a licensed HVAC technician is recommended for safety and warranty compliance.

When To Upgrade From Standing Pilot To Electronic Ignition

Electronic ignition systems eliminate continuous pilot flames, improving efficiency and reliability. Consider upgrading if the pilot keeps going out on furnace systems frequently, the furnace is older, or homeowners seek lower gas usage and fewer maintenance demands. Conversion costs are higher up front but can yield fuel savings and fewer service calls.

Frequently Asked Questions About Pilot Lights

Why Is My Pilot Light Yellow Instead Of Blue?

A yellow pilot suggests incomplete combustion, often due to dirt or low gas pressure. A properly burning pilot should be mostly blue with a small inner cone. Address yellow flames promptly to avoid soot and carbon monoxide risk.

Can A Thermostat Cause The Pilot To Go Out?

A thermostat rarely causes the pilot to go out. The thermostat signals the main burners; the pilot flame is controlled by the gas valve and safety sensors. Wiring faults between controls could indirectly affect operation but are uncommon.

Is It Safe To Relight A Pilot If It Keeps Going Out?

Relighting is safe if there’s no gas odor and the cause is known or being addressed. If relighting repeatedly is necessary or gas smell is present, stop and call a professional. Follow the furnace manufacturer’s relighting instructions carefully.

Key Takeaways

Pilot Light Issues Are Common And Often Fixable: Clogged pilot orifices and worn thermocouples are typical and frequently resolved with cleaning or replacement. Safety Is Paramount: Gas leaks, blocked vents, and malfunctioning gas valves require immediate professional attention. Maintenance Prevents Failures: Annual servicing and sealing drafts reduce the likelihood that the pilot keeps going out on furnace systems.

For persistent problems, complex repairs, or any suspicion of a gas leak, enlist a licensed HVAC technician to ensure safe, code-compliant service and restore dependable heating.