Pilot Light Is Out on Furnace: Troubleshooting, Safety, and Repair

The phrase “pilot out on furnace” often signals a heating interruption and potential safety concern. This article explains why a furnace pilot light goes out, how to relight it safely, diagnostic steps, when to call a professional, and preventive maintenance to avoid recurring pilot outages. The guidance applies to common gas furnaces in American homes and emphasizes safety and code-conscious practices.

Problem	Likely Cause	Quick Action
Pilot Light Out	Thermocouple Failure, Drafts, Dirty Pilot Orifice	Relight Pilot Per Manual, Check Thermocouple
Pilot Keeps Going Out	Faulty Thermocouple, Gas Valve, Drafts	Inspect Thermocouple, Seal Drafts, Call Technician
Gas Smell Near Furnace	Gas Leak	Evacuate, Call Gas Company/911

How A Furnace Pilot Light Works

A pilot light is a small, continuous flame that ignites the main burner when the thermostat calls for heat. In older furnaces the pilot remained lit continuously; many newer units use electronic ignition systems instead.

The pilot assembly includes the pilot orifice, a thermocouple or flame sensor, and a gas valve. The thermocouple senses flame and keeps the gas valve open; if it cools or fails, the gas valve closes and the pilot goes out for safety.

Common Causes For “Pilot Out On Furnace”

Understanding causes helps determine whether a homeowner can safely relight the pilot or needs a professional. Frequent pilot outages usually indicate a failing component or unsafe conditions.

• Faulty Thermocouple Or Flame Sensor: A worn or misaligned thermocouple will not register the flame, causing the valve to shut off gas. This is the most common cause for pilots that won’t stay lit.
• Clogged Pilot Orifice: Dust, soot, or spider webs can obstruct the pilot jet and produce a weak or unstable flame that fails to heat the thermocouple.
• Drafts Or Airflow Issues: Strong drafts from open windows, attic fans, or pressure imbalances can blow out the pilot flame.
• Gas Supply Problems: Low gas pressure, a closed gas valve, or issues with the supply line can prevent the pilot from lighting or sustaining.
• Old Or Malfunctioning Control Valve: The gas control valve can degrade over time, failing to supply steady gas to the pilot.
• Dirty Or Misadjusted Burner: Although related to the main burner, poor combustion conditions can affect pilot stability in some systems.

Safety First: When To Stop And Call For Help

Working with gas appliances carries risks. If any of these conditions exist, take immediate precautions and call a professional.

• Smell Of Natural Gas: If a strong gas odor is present, do not attempt to light the pilot. Evacuate the home, avoid using switches, and call the gas company or 911 from a safe location.
• Repeated Pilot Failures: If the pilot goes out repeatedly after relighting, the underlying problem needs a professional diagnosis.
• Unfamiliar Or Electronic Ignition Systems: Many modern furnaces use intermittent pilot or electronic igniters that require specialized troubleshooting.
• Visible Damage Or Corrosion: Any damaged gas lines, fittings, or rusted components should be handled by a certified HVAC technician or plumber.

How To Relight A Pilot Light Safely

Homeowners with basic mechanical aptitude can relight a pilot on older furnaces if safety checks are satisfied and no gas odor exists. Always follow the furnace manufacturer’s instructions in the owner’s manual.

1. Turn Off The Thermostat And Gas Valve: Set the thermostat to off and locate the furnace’s gas valve on the control panel; turn it to the “off” position and wait five minutes to clear any accumulated gas.
2. Inspect For Gas Odor: Confirm no smell of gas before proceeding. If gas is detected at any point, stop and call the gas company.
3. Access The Pilot Assembly: Remove the furnace access panel to reach the pilot light area. Use a flashlight to inspect for debris or spiders.
4. Turn The Gas Valve To “Pilot”: Position the valve to the pilot setting per the furnace manual.
5. Light The Pilot: Hold a long lighter or match near the pilot orifice, press and hold the pilot button/knob while igniting. Continue holding for 30–60 seconds to allow the thermocouple to heat.
6. Release And Observe: Release the pilot button; the pilot should remain lit. Turn the gas valve to “On” and replace the access panel. Set the thermostat to call for heat and observe burner operation.

Important Relighting Tips

• Use a long lighter or match to keep hands clear from flame and hot surfaces.
• If the pilot does not stay lit after several attempts, do not continue—shut off the gas and call a technician.
• Always follow the specific steps in the furnace owner’s manual; designs vary.

Diagnosing Persistent Pilot Light Problems

If relighting fails or the pilot won’t stay lit, follow a stepwise diagnostic approach to isolate the cause before replacing parts.

• Inspect And Clean The Pilot Orifice: Turn off gas and power, then gently clean the orifice and surrounding area using compressed air or a small brush. Avoid enlarging the orifice.
• Check The Thermocouple Alignment: The thermocouple tip should sit directly in the pilot flame. If bent away, gently reposition the thermocouple until fully immersed in the flame.
• Test Thermocouple Function: Thermocouples can be tested with a multimeter for millivolt output when heated. Low output indicates replacement is required.
• Examine For Drafts: Temporarily close nearby windows or doors, or block obvious drafts to see if the pilot stabilizes.
• Verify Gas Valve And Supply: Confirm the household gas supply is on and that other gas appliances operate normally. If multiple appliances are affected, contact the gas utility.
• Consider Age And Wear: Thermocouples and control valves have finite lifespans; repeated failures suggest replacement of worn components.

Repair Options And Typical Costs

Costs vary by location, furnace model, and whether parts require replacement. The following provides ballpark figures for the U.S. market for common fixes.

Service/Part	Estimated Cost
Thermocouple Replacement (Part + Labor)	$75–$250
Pilot Orifice Cleaning (Service Call)	$80–$150
Gas Control Valve Replacement	$300–$700
Full Furnace Service/Inspection	$100–$300

Prices are approximate. Thermocouple replacement is relatively inexpensive and is often the first repair to try if the pilot won’t stay lit.

When Electronic Ignition Replaces A Pilot Light

Many modern furnaces use intermittent pilot systems or hot surface/electronic ignition. These eliminate a continuous pilot light and have different failure modes.

• Electronic Ignition Modules: Can fail electrically and require diagnostic service or replacement.
• Hot Surface Igniters: Are fragile and break with age; replacement is a common repair on newer units.
• Advantages: Electronic ignition improves efficiency and eliminates the continuous gas use of a standing pilot.

If a homeowner searches “pilot out on furnace” and the unit has electronic ignition, the troubleshooting steps differ and a professional inspection is often required.

Preventive Maintenance To Avoid Pilot Out Issues

Regular maintenance reduces the risk of pilot outages and extends furnace life. Annual service before heating season is recommended.

• Schedule Annual HVAC Tune-Ups: A licensed technician can clean burners, inspect the pilot assembly, test thermocouples, and check gas pressures.
• Keep The Area Clean: Prevent spider webs and dust from accumulating near the pilot and combustion chamber.
• Check For Drafts: Seal gaps around the furnace room and ensure exhaust vents and house pressure are balanced.
• Replace Aging Components Proactively: Thermocouples and igniters show gradual wear; replacing them during service avoids emergency failures.

DIY Versus Professional Service: Decision Guide

Homeowners can safely relight a pilot if the manufacturer’s instructions are followed, no gas odor is present, and components are in good condition.

• Proceed With DIY If: The pilot went out once, there is no gas odor, and the homeowner can follow the manual’s relighting steps safely.
• Call A Professional If: There is a gas smell, repeated pilot outages occur, the furnace uses electronic ignition, or any gas lines/components show damage.

Relevant Codes, Regulations, And Safety Standards

Furnace installation and repairs in the U.S. are subject to local building codes and national standards such as the International Fuel Gas Code (IFGC) and NFPA 54 (National Fuel Gas Code).

Gas appliance work often requires licensed technicians to ensure compliance with safety and ventilation standards. Homeowners should check local rules before attempting significant repairs or replacements.

FAQs: Quick Answers About “Pilot Out On Furnace”

Why Does The Pilot Keep Going Out? Most commonly due to a failing thermocouple, dirty pilot orifice, or drafts. Persistent outages require professional inspection.

Can A Pilot Be Relit If There Is A Gas Smell? No. Evacuate and call the gas company or emergency services.

How Long Should A Pilot Flame Burn? A normal pilot flame is steady and blue with a small yellow tip; it should stay lit continuously on older systems.

Is Replacing The Thermocouple A Simple Repair? For those comfortable working with gas appliances and following safety steps, thermocouple replacement is a common technician task and sometimes DIY for experienced homeowners.

Should Homeowners Convert To Electronic Ignition? Converting may improve efficiency and safety but should be evaluated by a professional to ensure compatibility and code compliance.

Resources And Where To Get Help

• American Gas Association — Information on gas safety and industry practices.
• National Fire Protection Association (NFPA) — Codes and safety standards for gas appliances.
• Local Gas Utility — Many utilities provide emergency response for suspected leaks and can inspect service lines.
• Licensed HVAC Contractors — Use certified professionals (NATE-certified when possible) for repairs involving gas valves, control systems, or major components.

Following safe relighting practices, routine maintenance, and timely professional service helps resolve “pilot out on furnace” problems quickly and reduces the risk of repeat outages or hazards.