Understanding And Troubleshooting Your Furnace Pilot Light


Your natural gas furnace depends upon the pilot light to work properly. This small blue flame is constantly on, ready to fire the furnace when heat is needed. If the pilot light goes out, the entire furnace unit stops working. The following guide can help you better understand and diagnose problems with the pilot light.

What does the pilot light consist of?

The pilot light consists of a valve that allows a small amount of gas to escape and remain lit. This basically keeps the furnace primed so it can pop on and off without you needing to provide the initial spark each time. The second part of this system is the thermocouple. This piece consists of two different metals that produce a small amount of voltage when touched. It's this voltage that keeps the valve open and the small amount of gas flowing so the pilot remains lit. If the thermocouple fails, the valve closes and the pilot light goes out.

What do you do if the light goes out?

Sometimes pilot lights go out for no discernible reason. They may go out if the system isn't used for an extended period of time, or if something passes in front of the valve, such as dirt. You can relight a pilot light on your own if this occurs. The process is relatively simple on modern furnaces:

  1. Switch the pilot light switch on the furnace to off and wait a few minutes for any gas in the area to dissipate.

  2. Press and hold the reset button.

  3. While holding the button, light the pilot with a long match or barbecue lighter.

You may also want to check the owner's manual, as some furnaces do not need a lighter and they produce their own ignition spark when the reset button is pushed.

How do you you troubleshoot a pilot that won't remain lit?

If you pilot light continues to go out or if you notice other issues, such as an unsteady flame or a flame that burns any color other than blue, there may be an actual problem in the system.

Unsteady flames or those that are burning red or orange often result from dirt at the mouth of the gas valve. You may be able to fix this on your own by turning off the furnace and pilot light, and then allow the gas to dissipate. Check that there are no obstructions near the gas valve – even dust or hair can result in flame issues. You can also insert just the tip of a metal wire into the valve to clean out any residue that could be causing problems.

For pilots that won't remain lit, you may have a faulty thermocouple, which will need to be replaced. Contact a heating repair contractor like one from Controlled Comfort in your area if you continue to experience problems with the pilot light so they can locate and fix the issue.

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