How to replace a hot surface igniter
- Takes about 20 minutes
- Beginner-friendly
- 2 tools needed
- Updated
- Reviewed by a licensed tech
A cracked or worn-out igniter is the single most common reason a modern gas furnace clicks, hums, and never lights. It is a twenty-minute swap with one nut driver, and the part costs less than a service call's first fifteen minutes.
Safety
Kill power at the service switch AND the breaker before the door comes off. The igniter runs at 2,500°F and the element is as brittle as a pencil lead — never touch it, even stone cold: the oil from your fingertips bakes into a hot spot and cracks it on the next cycle.
What you'll need
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¼ in nut driver
The one screw holding the bracket. A magnetic tip saves you fishing it out of the burner box.
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Phone camera
For the wiring photo in step 2. This is not a joke — it is the most useful tool on the list.
The fix, step by step
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Kill power and open the burner compartment
Flip the service switch on the furnace, then the breaker at the panel — both, not either. Most lower doors lift off their tabs without tools; a few have two screws along the bottom lip.
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Photograph the wiring, then unplug
One photo saves every "which wire went where" moment an hour from now. The igniter's plug pinches to release — squeeze the tab and pull on the connector body, never on the wires.
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Check the old element before you swap it
Set a multimeter to ohms across the igniter's two pins with the plug still out. A healthy silicon nitride element reads roughly 40–70 Ω cold; a silicon carbide one reads 40–90 Ω. Infinite resistance means it is open and it is definitely your fault. In range means the igniter is fine and your problem is somewhere else — stop here and check the flame sensor first.
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Swap the igniter — bracket for bracket
One ¼ in screw holds it. Match the new element's bracket to the one you took out — the kit ships six because the mount pattern is what varies between furnaces, not the element. Hold the new igniter by its ceramic base only, and seat it so the element sits in the same spot in the flame path the old one did.
Safety: If the old element is shattered, sweep the burner box out before the new one goes in. Ceramic fragments in the burner tubes will glow, hold heat, and crack the replacement.
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Restore power and watch one full cycle
Door back on — most furnaces have a door switch and will not fire without it. You should see a steady orange glow for about 17 seconds, then ignition, then the burners staying lit after the igniter fades. Three failed tries puts the board into lockout; if that happens, the flashing LED behind the sight glass is telling you what it saw.