Why Did My Furnace Pilot Light Go Out and How Do I Relight It?

By Laurie M Nichols

Updated on Jan. 05, 2024

Learn all about your furnace pilot light — where it is, what it does, and how to troubleshoot the most common issue.

If you heat your home with natural gas, oil or propane, chances are your furnace or boiler has a pilot light. With the help of two experts — Joshua Smith from Berkshire Heating and Cooling and Alexander Siv from Amherst Plumbing and Heating — learn what a pilot light is, some reasons it may go out, and what to do if it does.

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A pilot light is a small flame that’s constantly lit within a gas furnace. It’s the ignition source for the main gas burner when it’s activated by the thermostat. Other gas appliances like stoves, ovens and water heaters may also have pilot lights.

Electric furnaces do not have a pilot light. And starting around 2010, gas furnaces haven’t, either.

“Pilot lights are an older technology,” Smith says, “Modern gas furnaces use a hot surface ignition source that relies on electricity.” But there are still plenty of pilot light ignition systems still in use.

There can be several reasons why your pilot light is out:

You’ll need to do a visual inspection. Consult your furnace owner’s manual to determine the pilot’s exact location. Most are near the bottom of the furnace, behind a removable access panel.

Take off the panel and look for a small bluish flame. If there’s no visible flame, your pilot’s out.

Here’s another obvious sign: You turn up the thermostat but your house stays cold. “You’ll have no heat because the pilot’s not there to ignite the burner,” Smith says.

No. The thermocouple will stop detecting heat and shut off the gas valve.

It depends. “Anyone can relight a pilot,” Siv says, “but the reason your pilot light went out in the first place will determine if it’s able to be relit.”

If it’s due to a bad thermocouple or gas valve, these will need to be repaired first. Also, if the pilot light orifice is clogged, it will need to be cleaned before relighting will be successful.

The pilot lighting instructions should be right on the equipment. If you’re not comfortable relighting your pilot, call an HVAC pro to do it for you.

If you know why your pilot light is out, and you feel confident in your skills and abilities, here are steps to relight a pilot light. Make sure to consult with your furnace’s owner’s manual for more detailed instructions.

If the flame doesn’t stay lit or needs to be manually relit often, Siv says this indicates a mechanical problem with the thermocouple or gas valve. “It’s best to call in a pro at that point,” he says.