How to Replace a Furnace Igniter

Furnace igniters fail quietly. One day your heat stops working, you hear the blower trying to start, and nothing catches. The igniter is a ceramic or metal component that glows hot enough to ignite the gas burners—and when it ages, it loses that ability. Replacing one is straightforward enough for a confident homeowner, but this isn't a project for someone uncomfortable with gas equipment. The work takes an hour, costs far less than a service call, and you'll have heat again by evening. What matters most is following the safety sequence: kill the power, kill the gas, wait for the furnace to cool, then work methodically. Rush it and you risk damage or a dangerous misfire when you restart.

  1. Kill Power First. Locate your furnace breaker in the electrical panel and switch it to OFF. Then set your thermostat to OFF (not heat mode). Wait 5 minutes for the furnace control board to de-energize completely. This prevents accidental ignition or electrical shock while you work.
  2. Shut Off Gas. Find the gas supply line leading to your furnace. There's a shut-off valve (usually a lever handle or round knob) on that line. Turn the lever 90 degrees (perpendicular to the pipe) or turn the knob clockwise until it stops. You'll feel definite resistance. Do not force it.
  3. Document Everything First. Open the furnace access panel (usually held by two clips or a latch). You'll see the burner assembly inside. The igniter sits just above or beside the burners—it's a thin ceramic or metal rod, roughly 2–3 inches long, mounted on a bracket. Before you remove anything, photograph the igniter's position, the electrical connector, and any surrounding parts. This reference is invaluable when reassembling.
  4. Unplug Igniter. The igniter has a small plastic electrical connector clipped to its terminal wires. Gently pull that connector straight off. Don't yank the wires themselves. If the connector is stiff, wiggle it side to side while pulling. Once free, tape the bare wire terminals to the bracket with electrical tape so they don't touch anything metal.
  5. Extract Old Igniter. The igniter is held to a bracket by one or two small bolts (usually 1/4-inch). Use your wrench or socket to loosen and remove these bolts completely. Lift the old igniter straight out. Don't force it—if it sticks, check that both bolts are fully removed. Handle the old igniter carefully; ceramic igniters shatter if dropped.
  6. Mount New Igniter. Position the new igniter in the same location as the old one, aligning the mounting holes with the bracket. Insert the bolts and tighten them finger-tight first, then use your wrench to snug them—firm but not crushing. The igniter should sit in the exact same spot relative to the burners as it did before.
  7. Reconnect Power. Remove the electrical tape from the terminal wires. Clip the connector back onto the igniter terminals, making sure it seats fully—you should hear a slight click. Gently tug the connector to confirm it's locked. Close the furnace access panel and secure the clips.
  8. Restore Power and Test. Turn the gas shut-off valve handle back parallel to the gas line (ON position). Return to the electrical panel and switch the furnace breaker back to ON. Set your thermostat to HEAT and a temperature above room temperature. Listen for the igniter to spark—you'll hear a soft clicking for a few seconds, then a whoosh as the burners light. The blower should follow within 30 seconds.