How to Light a Furnace

Co-authored by wikiHow Staff

Last Updated: January 31, 2022

You go to turn on your furnace on a cold winter day and it doesn’t start. If you’ve got an old school furnace with a pilot light, it may be a sign that it needs to be relit. Don’t worry; this is not a difficult or dangerous fix, and there’s no need to spend money calling a repair person out. So long as you follow the instructions we’ve compiled below, you'll be warm and cozy again in no time.

Part 1

Part 1 of 2:

Checking and Preparing the Furnace

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Check the power. Before you try and relight it, do some basic checks on your furnace. Make sure it’s connected to the electric and gas sources. It could be that your furnace is working and it's actually your thermostat that needs new batteries.^{[1]
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2
Find your pilot light and check if it’s gone out. The pilot light is a small burner that lights the larger furnace burners, and you can usually find it at the bottom of the furnace. If it's on, you should be able to see a small flame. Your pilot light might have gone out from a draft, and you’ll need to relight it to get your furnace working again.^{[2]
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3
Turn off the furnace and wait five minutes for the gas to dissipate. Find the switch near the bottom of your furnace, which normally says “pilot,” “on” and “off.” Once you’ve turned it off, you have to wait for five minutes so that all the gas can dissipate. Otherwise, it could be dangerous to try and relight the pilot light.^{[3]
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- If you can’t figure out how to turn it off, check the instructions label on the furnace.
- If you can smell gas, don't relight the pilot!

Part 2

Part 2 of 2:

Relighting the Pilot

1
Relight the pilot light with the ignition button, if your furnace has one. If you can’t find the ignition button, check the instruction sticker on your furnace or the the owner’s manual. The ignition button will usually will have a small red button next to it. Press the small button while you press the electric ignition. The pilot light should light, but keep holding the small button down for about a minute.^{[4]
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2
Re-light the pilot light with a flame if it doesn’t have an electric ignition. Turn the switch or knob to “Pilot” and hold down the reset button. With a long lighter, bring a flame close to the pilot light opening. This isn't very dangerous, but you should use caution. Once the pilot light has caught and is burning brightly, you can release the reset button.^{[5]
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- If you don’t have a long lighter, you can use a long match, but don’t use a regular size lighter or match. You want to keep some distance between you and the flame!
- You may have to try to light the pilot two or three times.
3
Turn on your furnace and wait to see if it works. If the pilot light goes out, the pilot light opening might be clogged. To clean it, you can turn off the gas, wait five minutes, and then clean the opening with fine wire.
- If it’s still not working even after you’ve lit the pilot light, then something else is wrong with it. You may want to contact someone who specializes in furnaces to help you fix it. ^{[6]
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