What is a furnace igniter?
Updated August 2026
A furnace igniter is the element that glows orange-hot to light the gas burners every time the furnace starts. Nearly every gas furnace built since the early 1990s uses one instead of a standing pilot light, which burned gas around the clock. The common design is the hot-surface igniter: a brittle silicon-carbide or silicon-nitride element about the size of a paperclip, mounted on a ceramic block, that reaches 1,800 to 2,500 degrees in 20 to 45 seconds. Some furnaces use a spark igniter instead, which clicks like a gas grill.
Where it is
It lives behind the lower front panel at one end of the burner assembly, aimed at the first burner port, with a two-wire plug running back to the control board. The easy way to identify it is to watch a startup: the draft inducer fan spins up for 30 to 60 seconds, a small element begins to glow behind the burners, then the gas valve opens with a soft whoosh. A cracked igniter usually still looks whole, so hold it toward a light and hunt for a hairline break across the element. Never touch that element with bare fingers, because skin oil bakes into a hot spot and cracks it.
What it does
Silicon carbide is a ceramic, which means it is hard and it is fragile. Every heating cycle takes the element from room temperature to white heat and back, and after 3 to 7 years of that treatment it fractures. During a cold snap, with the furnace cycling 6 to 8 times an hour, a marginal igniter picks that night to go. The failure reads the same in every house: the inducer runs, nothing glows, gas never opens, the board tries three times, and the furnace locks out with a blinking code. There is no partial failure and no warning noise, so heat simply stops. Techs keep these on the truck because nothing else in a furnace breaks this predictably.
Maintenance
An igniter is a wear part, not a cleanable one, so the maintenance is inspection and timing. Have it checked at the annual fall tune-up, and consider a planned swap around the 5-year mark or when a technician sees its resistance drifting, instead of waiting for a January lockout. Keeping the burners and the flame sensor clean helps indirectly, since a furnace that fails to light and retries piles extra cycles onto the element. The numbers behind the interval are in how often to replace a furnace igniter and how long a furnace igniter lasts.
What it costs to replace
A replacement furnace igniter runs $15–50 for the part, or $150–350 installed on a service call.
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Frequently asked questions
How do I know if my furnace igniter is bad?
Two checks settle it. First, watch a start cycle: if the inducer runs but nothing behind the burners glows within about 45 seconds, the igniter is the prime suspect. Second, with the power off, unplug it and put a multimeter across the two leads; a working element shows continuity, and a dead one reads open. Look for a hairline crack while it is out of the furnace. A unit that lights and then dies a few seconds later has a different fault, usually a dirty flame sensor.
Can I replace a furnace igniter myself?
It is a 30 to 45 minute job for someone comfortable around a gas appliance. Shut off power at the furnace switch and the breaker, photograph the wiring, unclip the plug, remove one or two screws, and seat the new element holding only its ceramic base. The part has to match, since silicon-carbide and silicon-nitride igniters are not interchangeable, so order by furnace model or part number. Step by step: how to replace a furnace igniter.
Why do my furnace igniters keep failing?
A failure every year or two means something upstream is stressing the element. Usual suspects: high line voltage (anything over about 125 volts cooks igniters), short-cycling caused by a clogged filter or an oversized furnace, a control board holding power on too long, and cheap aftermarket parts. Handling a new one by the element does it too. If the third igniter in three winters just quit, have someone measure voltage and cycle counts. More on the symptom: why a furnace igniter is not glowing.
Is a hot-surface igniter the same as a pilot light?
No. A standing pilot is a real flame that burns continuously and lights the burners on demand, costing a few dollars a month in gas. A hot-surface igniter only draws power for 20 to 45 seconds per cycle, then shuts off, which is why it replaced pilots on almost all furnaces from the 1990s onward. The tradeoff: pilots rarely break, while igniters are a scheduled replacement every 3 to 7 years.