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The Furnace Pilot Light Keeps Going Out

February 8, 2023 | Blog

The pilot light of a furnace can help warm an entire house, but it may go out occasionally. We will look at why this happens, how to relight it, and provide some safety tips and maintenance advice for the pilot light and furnace.

What is a Furnace Pilot Light

A pilot light is a small gas flame used in older furnaces as an ignition source for the furnace’s gas burners. It’s a perpetual flame, ready to start the burners when the thermostat tells them to turn on.

furnace pilot light

3 Reasons Pilot Light Keeps Going Out

1. Pilot Light is Dirty

The pilot light opening, also called the pilot orifice, should be clean to develop a strong flame. Over time, the opening may fill with dirt, dust, and other minute debris. To clean, turn off the furnace, disconnect the power source, and disassemble the pilot light. Use compressed air or a needle to knock the dirt from the opening then reassemble.

2. Thermocouple Fails (broken, dirty, or off center)


The thermocouple, or flame sensor, is the safety mechanism that shuts the gas supply off if the pilot light goes out.

  • Broken or burned out: Over time, the copper rod may break or burn out and is unable to correctly sense the lit flame. Until it’s replaced, the thermocouple stops the gas flow from the gas valve.
  • Dirty: Soot, ash, and other dirt can build on the thermocouple and interfere with its function. But it’s easy to clean — remove the thermocouple and use a wire brush or coarse object to brush away the debris then reinstall.
  • Misaligned: Make sure the flame fully envelops the top of the thermocouple. If the rod is misaligned, it can’t read the flame and triggers the gas valve shutoff.

3. Drafty Basement or Attic

If your furnace is located in an attic an area known for air drafts, it is important to check the area for drafts and seal any air leaks. Even a small amount of air can blow out the pilot light. Additionally, make sure that the air intake registers in the home stay open and unobstructed to ensure proper air flow.


How to Re-Light Pilot Light

It’s relatively easy to re-light a furnace pilot light if there isn’t a larger issue within the system. However, if you suspect a broken part or leak anywhere in the heating unit, contact an HVAC professional immediately.


Check the Manual

If you cannot locate your furnace manual, you should try searching the internet for instructions specific to your model. You can also contact the furnace manufacturer to see if they can provide the manual either by regular mail or email.

Turn off the Gas

For your safety and the safety of anyone else in the house, turn off the gas and leave it off at least five minutes before proceeding. This time should be enough to allow leftover gas in the valves to dissipate.

Reset the Gas and Light the Pilot Light

Turn the gas back on and allow it to release from the pilot light. Look for a dial with a ‘pilot’ option to also restart the gas flow, and a separate reset button. Press the reset button and use a long lighter, such as a gas grill lighter, to relight the pilot light.

Pilot Light Safety and Maintenance Tips

Any appliance, such as a furnace, that relies on gas to operate should be approached with care. As with any part of an HVAC system, regular tune-ups and maintenance performed by a trained technician is key to the longevity and safety of a furnace.

Schedule Routine Tune-Ups and Maintenance

In their prime, furnaces with pilot lights could operate with 50% to 70% efficiency. Regular maintenance is the best way to extend the efficiency, and safety within your home.

During a regular tune-up, an HVAC technician checks the furnace’s performance, how much carbon monoxide it produces, and cleans the unit. When the furnace operates, the internal heat exchanger collects dirt and other debris; as the debris builds, the furnace has to work harder to produce heat, increasing overall wear and tear.

Make sure to Change Your Air Filter

The air filter protects the blower fan from collecting airborne debris, such as dust, fur, and hair, that can build and clog its movement. Plus, the filter stops the debris from recirculating in your home, improving the indoor air quality.

air filter

Place Carbon Monoxide Detectors in Bedrooms

As furnaces age, they can produce increased amounts of carbon monoxide, an odorless and poisonous gas. To ensure safety, it is advised to install carbon monoxide detectors in bedrooms and any other areas used for sleeping. If a detector is triggered, evacuate the premises immediately and contact 911.

carbon monoxide alarm

You may need to relight a pilot light at an inopportune time, but regular maintenance and system tune-ups should keep the activity at bay. Schedule a furnace tune-up with Service Wizard today.

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