How to Reset a Pilot Light on a Furnace

The pilot light on a furnace is a small flame that ignites the main burners. When it goes out, the furnace won’t heat, and resetting the pilot light safely restores operation in many cases. This guide explains how to reset a pilot light on a furnace, common causes, troubleshooting steps, safety tips, and when to call a professional.

Quick Steps	What To Do
1	Turn Off Gas And Wait 5 Minutes
2	Locate Pilot Assembly And Controls
3	Follow Manufacturer Lighting Procedure
4	Observe Flame And Thermocouple

How Pilot Lights Work

A pilot light is a small, continuously burning flame used to ignite the main burners in many older gas furnaces. The thermostat calls for heat, the gas valve opens, and the pilot lights the burner. Modern furnaces often use electronic ignition systems instead of a standing pilot light.

Key components include the pilot orifice, thermocouple (or thermopile), pilot tube, gas valve, and ignition control. The thermocouple senses the pilot flame and allows the gas valve to stay open; a weak or misaligned thermocouple will shut the valve for safety.

When To Reset The Pilot Light

Resetting the pilot light is appropriate when the furnace has a standing pilot and the flame has gone out due to drafts, temporary gas supply interruptions, or after maintenance. It is not recommended for furnaces with electronic ignition systems.

Do Not Attempt to relight if there is a strong smell of gas, a suspected gas leak, or if the furnace repeatedly loses its pilot light after relighting.

Safety Precautions Before Resetting

Safety is critical when working with gas appliances. Always follow these precautions before attempting to reset a pilot light on a furnace.

• Turn off the furnace power at the thermostat and main switch.
• Shut off the gas supply to the furnace using the shutoff valve and wait at least five minutes for gas to clear.
• Ventilate the area by opening windows and doors if there is any gas odor.
• Have a multi-purpose fire extinguisher nearby and avoid open flames while working.
• Wear safety glasses and use a long-reach lighter or match if manual ignition is required.

Tools And Materials Needed

Most resets require only common items. Having these prepared reduces time and risk.

• Long-stem lighter or fireplace matches
• Screwdriver or nut driver (to access burner compartment)
• Flashlight
• Needle-nose pliers
• Adjustable wrench (for gas valve if necessary)

Step-By-Step: How To Reset A Pilot Light On A Furnace

Locate The Pilot Assembly

Open the furnace access panel and identify the pilot assembly, which usually sits near the gas control valve and main burner. The pilot has a small metal tube and a blue or yellow flame when lit.

Turn Off Gas And Power

Switch the furnace control to OFF and turn off the gas valve at the appliance. Wait at least five minutes to let any accumulated gas dissipate before proceeding. This reduces the risk of ignition flashes.

Access The Pilot And Clean If Needed

Clear dust and debris around the pilot area with compressed air or a soft brush. A blocked pilot orifice can prevent reliable ignition. Use a thin wire carefully to remove buildup without enlarging the orifice.

Follow The Manufacturer Lighting Procedure

Most furnaces display a lighting instruction label inside the access panel. Typical steps: turn the gas knob to PILOT, press and hold the knob down, light the pilot with a long lighter, hold the knob for 30–60 seconds to warm the thermocouple, then release and turn the knob to ON if the pilot stays lit.

Observe The Flame

A healthy pilot flame is steady and blue with perhaps a small yellow tip. It should envelop the thermocouple. If the flame is weak, misdirected, or mostly yellow, adjust the pilot alignment or clean the orifice and try again.

Restore Power And Test Furnace

After the pilot stays lit and the gas valve is set to ON, replace the access panel, restore power at the switch and thermostat, then set the thermostat to call for heat. The furnace should ignite the main burners within a minute or two.

Troubleshooting: Pilot Light Won’t Stay Lit

If the pilot light won’t stay lit after following proper reset steps, consider these common causes and checks.

• Faulty Thermocouple: The thermocouple senses the flame and keeps the gas valve open. Replace if it’s corroded or fails continuity testing.
• Pilot Orifice Blockage: Dirt or spider webs can block the orifice. Clean carefully with compressed air or a small wire.
• Drafts Or Airflow: Strong drafts from nearby vents, fans, or open doors can extinguish the pilot. Adjust shielding or address airflow issues.
• Gas Supply Problems: Ensure the gas service is active and the valve supplying the furnace is open.
• Worn Gas Valve Or Controls: Electronic or mechanical failures in the gas valve or control module may require replacement by a technician.

How To Test The Thermocouple

Testing a thermocouple helps determine if it’s the likely cause of a pilot that won’t stay lit. A multimeter measures millivolts produced when heated by the flame.

1. Remove the thermocouple from the gas valve while keeping the tip in the pilot flame.
2. Set the multimeter to millivolts (mV); heat the thermocouple tip with the pilot flame.
3. A healthy thermocouple should produce about 20–30 mV or higher. Significantly lower readings indicate replacement is needed.

Preventive Maintenance To Keep Pilot Lit

Regular maintenance reduces the chances of pilot light failure and improves furnace longevity.

• Schedule annual professional furnace inspections and tune-ups.
• Keep the area around the furnace clean and free of dust and debris.
• Check and replace the air filter every 1–3 months to maintain proper airflow.
• Inspect venting and combustion air openings to prevent drafts or blockages.
• Lubricate any accessible fan bearings and check belts as part of seasonal maintenance.

When To Call A Professional

Call a licensed HVAC technician or gas service professional if any of the following apply.

• Persistent pilot outages after multiple relighting attempts.
• Strong or persistent smell of gas; leave the area and contact the gas utility immediately.
• Visible corrosion on the thermocouple, gas valve, or pilot assembly.
• Gas control valve or ignition control failure.
• Unfamiliar noises, soot, yellow sustained flames, or carbon monoxide concerns.

Common Mistakes To Avoid

Avoid actions that increase risk or damage furnace components.

• Do not attempt to relight the pilot without waiting for gas to clear after shutting off the supply.
• Never force or enlarge the pilot orifice; small parts are precisely sized.
• Avoid using makeshift tools or open flames too close to the appliance.
• Do not ignore repeated pilot outages — underlying issues may be dangerous.

FAQs About Resetting A Pilot Light On A Furnace

Is It Safe To Relight The Pilot Light?

Relighting is safe when safety steps are followed: shut off gas, wait five minutes, ventilate, and follow the manufacturer’s procedure. If a gas smell is present, evacuate and call the gas company.

How Long Should A Pilot Light Stay Lit?

A properly functioning pilot should remain lit continuously. If it goes out frequently, the cause may be a faulty thermocouple, draft issues, or a gas supply problem.

Can A Furnace Pilot Light Cause Carbon Monoxide?

A properly burning blue flame produces minimal carbon monoxide. A yellow, lazy flame or incomplete combustion can indicate a problem that could increase carbon monoxide risk. Have a professional inspect the furnace and install a carbon monoxide detector nearby.

What If The Furnace Has Electronic Ignition?

Many modern furnaces use electronic ignition and do not have a pilot light. For ignition failures in these systems, issue diagnosis and repair usually require a professional technician.

Additional Resources And References

For more information, consult furnace manufacturer manuals, the U.S. Consumer Product Safety Commission, and the Environmental Protection Agency’s guidance on indoor air and combustion appliances. Homeowner forums and HVAC resources can offer practical tips, but professional service is recommended for gas-related repairs.

Reminder: When in doubt, prioritize safety and call a licensed HVAC technician or the gas utility for suspected leaks or persistent issues with resetting a pilot light on a furnace.