Come On Baby, Re-Light My Fire – How to Replace A Furnace Ignitor

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It’s Friday night, eight o’clock, and it’s getting cold and nasty outside. You just ordered a pay-per-view movie, the popcorn is ready, and you just nudged the thermostat up a degree or two to make your cinematic experience a bit cozier. Then you notice, hey, it’s actually getting CHILLIER in here! You listen as the furnace kicks on, feel it blowing cold air for 15 seconds or so, and then hear it shut down. You grab a fleece and mutter a string of R-rated words to yourself as you look up the number for the 24-hour furnace repair place, wondering how much an after-hours service call is going to set you back. 

But wait, there’s an alternate ending available! You remember that you read this fascinating article on HomeFixated about replacing your furnace’s hot surface ignitor, and wisely bought one to have on hand for just such an unhappy, but inevitable, occasion. You follow the simple instructions, and fifteen minutes (and a whole lot less moola) later, you’re curled up warm and happy, with your movie playing, your popcorn and Raisinettes littering the carpet, and your loved ones gazing at you in awe and admiration.

Feel The Burn

Typical condo furnace, jammed into a closet
Typical condo furnace, jammed into a closet

When it comes to working on your furnace, there probably aren’t a lot of problems you can resolve yourself, beyond keeping the filter clean. They’re complex pieces of machinery, filled with lots of electronic modules and other mysterious components, and it’s generally not a good plan to mess with something that can blow up unless you’re pretty sure about what you’re doing. How to replace a furnace ignitor is perhaps one exception to this rule; it’s pretty straightforward, and with modest DIY skills and a dose of caution, this is a task many can easily handle. With that said, if you don’t consider yourself competent enough to work with gas appliances, then it’s probably time to bite the bullet and call that 24 hour repair service.

Gas furnaces used to have standing pilot lights, which burned constantly, waiting patiently for the thermostat to call for heat. When it did, the gas would whoosh out, the pilot light would ignite the gas and make a nice big hot flame from the burners, and warm air would ensue. Standing pilots wasted a lot of gas, though, and over the past couple of decades have been phased out, replaced by electronic ignitions of various types.

This ignitor's ready for its dirt nap
This ignitor’s ready for its dirt nap

Chances are if your furnace was made in the last 25 years or so, it makes use of a hot surface ignitor to get the gas burning. When the thermostat calls for heat, the ignitor heats up and glows red-hot, then the gas valve opens, and the gas is ignited as it passes over the ignitor’s surface. These ignitors are fairly delicate, though, being made of ceramic, and after a few years of making gas go Kablooey they are ready for the used appliance parts scrap heap. It is rumored they are pre-programmed to do so only after 5 p.m, on the coldest day of the year, and preferably on a Saturday night or Christmas Eve.

Keep a Hot Surface Ignitor On Hand

Furnace spec sheet--hope your eyes focus better than my camera...
Furnace spec sheet–hope your eyes focus better than my camera…

If you can convince a local plumbing supply company to sell it to you, you can probably save a few bucks on the part. Many will only sell to licensed plumbers or HVAC technicians, but sometimes they’ll make an exception, especially if you come in looking forlorn and pathetic, and have a good story about your 97-year-old granny, drooling and frozen to her rocking chair. If not, internet retailers aren’t so finicky about who they sell to. Got a credit card? Here’s your ignitor! And a box of TNT! In either case, it’s a good idea to get one BEFORE the old one dies, unless you don’t mind a few days without heat. Wherever you buy it from, you’ll need the make and model number, which you’ll normally find on a spec sheet behind the cover panel on the front of the furnace.

While you’re checking for the model number on your furnace, give it a quick look to see if it has any other issues. It will run a lot more efficiently with a clean filter; get a couple of new ones if it uses the disposable type, or give it a good cleaning if it’s a permanent filter. You should also take a look at the exhaust venting, to make sure it’s firmly attached, and without leaks. When I went to replace the ignitor on the furnace for this story, I discovered that the vent pipe was unbelievably corroded, with a huge hole in it. I pointed it out to the homeowner, who then said she had been very sluggish, dizzy and headachy lately; that’s what carbon monoxide does to you, and if it goes on long enough, it’ll kill you. And that’s a BAD alternate ending! I put a new piece of pipe in, told her she should probably check with her doctor, and got her a carbon monoxide detector for added protection and peace of mind.

Can you spot the leak?
Can you spot the leak?

From Zero To Hero – How to Replace a Furnace Ignitor

When your world goes cold, take a look and see if there is a glow coming from within when the furnace is trying to start up. If you don’t see one, the time to get re-ignited is upon you. The only tools you need are a screwdriver or a ¼” nut driver. Here’s what to do:

First, make sure the power is OFF. Many furnaces have a switch adjacent to them for this purpose; if yours doesn’t, turn it off at the breaker box.

Shut the power off at the furnace or breaker box
Shut the power off at the furnace or breaker box

Pull the front cover off, and look for the burners; that’s the neighborhood your ignitor resides in. Most ignitors have a white base, and grey prongs with a rough texture. There will be two wires coming off the ignitor, with a wiring connector clip a few inches down. Squeeze the sides of the clip, and unplug it. The ignitor will be held in by a screw; unscrew it, and remove the old ignitor

Squeeze the sides of the clip to disconnect it

Get your new ignitor out. Note: these things are VERY fragile. Don’t bang it into anything, and don’t touch the ceramic prongs with your bare hands, or you’ll be doing this again in a few days. Use the old screw and GENTLY snug it up on the new ignitor. DON’T OVER-TIGHTEN!

GENTLY snug up the screw on the base of the new ignitor!
This is what happens if you over-tighten the screw...
This is what happens if you over-tighten the screw…
Replace the cover, restore power, flame on!
Replace the cover, restore power, flame on!

Insert the connector into the wiring clip, replace the front cover, and turn the power back on. Set the thermostat to your desired degree of coziness, and listen for the furnace to fire up. Verify that there’s actually HEAT coming from your furnace, bask in the glow of your admiring audience, and let the cinematic experience resume!

If you can’t buy an ignitor locally, they’re readily available from online parts outlets and


Photo of author

About Phil

Phil’s path to the pinnacle of success as HomeFixated’s Senior Writer was long and twisted. At various stages of his life, he worked as a framing carpenter, attended motorcycle mechanics school, served as an Army MP, did a hot and itchy stint installing insulation in Phoenix, owned and operated a small contracting firm doing residential renovations, and worked as an employee of a major airline (Motto: We’re not happy ‘til YOU’RE not happy). He is currently semi-retired, but continues to take on little projects, such as the total renovation of an old farmhouse. Yes, he is a slow learner. Future projects include a teardown restoration of his 1965 BMW motorcycle, and designing and building a kick-ass playhouse for his grandsons. Phil loves spending time outdoors, hanging out with family and friends, cool tools, and a cold IPA when beer o'clock rolls around.

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6 thoughts on “Come On Baby, Re-Light My Fire – How to Replace A Furnace Ignitor”

  1. Thank you for making a frustrating situation understandable and fun! I needed a little humor while trying to figure this out. I am that Grandma…minus the drool?…and feel like I can score the part and do this project! I really appreciate your post.

    • Glad the post was helpful, Kathy. Also happy to hear that you’re drool-free; getting drool on your new ignitor probably wouldn’t end well… Good luck, and let us know how you make out!

    • Usually if it makes a difference, the connectors will only attach in one orientation. If they’ll go together either way, it shouldn’t matter.

  2. I like to get my parts from an appliance parts house. They usually have no trouble selling to the public. People come in all the time for knobs and doo-dads for ovens, washers, and dryers but they also stock all the parts for more intricate appliance repair (like furnace and A/C parts).

    Although the Fergusons (plumbing supply) near me have no issue selling to the public either.

    • I’ve always been able to get them to sell to me, but sometimes I have to endure the “You’re not an HVAC tech” stinkeye while I wait. I get over it pretty quickly, though.


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