Step-by-step fix
Step 1: Confirm the igniter is the likely problem
- Set the thermostat to call for heat and listen to the furnace startup sequence.
- Watch through the burner view port or with the burner panel removed only if it is safe to do so.
- A typical failed igniter symptom is this: the inducer starts, you may hear a click, but the burners never light.
- Turn off power to the furnace before touching anything inside.
- Open the burner compartment and inspect the igniter for a visible crack, white blistering, or a broken tip.
If it works: The furnace acts like it is trying to light, but the igniter is damaged or never glows, making replacement a reasonable next step.
If it doesn’t: If the furnace has no power, no inducer startup, or a different fault pattern, troubleshoot the power supply, thermostat call, door switch, or control fault before replacing the igniter.
Stop if:- You smell gas before or during startup.
- The burner area shows melted wires, scorch marks, or heavy rust damage.
- You are not sure which part is the igniter or cannot safely access it.
Step 2: Shut the furnace down and access the igniter
- Turn the furnace power switch off or switch off the furnace circuit at the breaker.
- Close the gas shutoff valve if it is in the immediate work area and easy to identify.
- Remove the furnace access panel covering the burner compartment.
- Use a flashlight to locate the igniter near the burners. It is usually mounted at the burner assembly with one or two wires leading back to a plug.
If it works: Power is off, the burner area is open, and you can clearly reach the igniter and its connector.
If it doesn’t: If the panel will not come off or the igniter is buried behind other components, stop and look for a service manual inside the panel or consider a technician visit.
Stop if:- You cannot positively identify the furnace power disconnect or breaker.
- The gas shutoff valve is damaged, leaking, or hard to operate.
- Access requires removing sealed gas train parts or disturbing burner alignment.
Step 3: Remove the old igniter carefully
- Take a photo of the igniter position, wire routing, and connector before removing anything.
- Unplug the igniter connector or disconnect it at the harness without pulling on the wires themselves.
- Remove the mounting screw or screws holding the igniter bracket.
- Lift the igniter straight out gently. Handle it by the ceramic base or bracket, not the heating element.
- Compare the old igniter to the new one for overall shape, bracket style, connector style, and insertion depth.
If it works: The old igniter is out without damaging nearby burner parts, and the replacement appears to match.
If it doesn’t: If the new igniter does not match the old one closely enough to mount securely and reach the connector properly, pause and get the correct replacement.
Stop if:- The old igniter is stuck in place and forcing it may damage the burner assembly.
- The replacement requires modifying gas components or drilling new holes in the burner assembly.
- The wiring insulation is brittle, burned, or falling apart.
Step 4: Install the new igniter
- Hold the new igniter by the ceramic base or bracket only.
- Avoid touching the igniter element with bare fingers if possible. If you do touch it, wipe only as directed by the part instructions.
- Set the new igniter into the same position as the old one so the tip sits in the same area near the burner path.
- Reinstall the mounting screw snugly without overtightening the ceramic base.
- Reconnect the wiring and route it away from the burner flame, sharp edges, and moving parts.
If it works: The new igniter is mounted firmly, aligned like the original, and connected with safe wire routing.
If it doesn’t: If the igniter will not sit in the original position or the connector does not fit securely, remove it and verify you have the right part before powering the furnace back on.
Stop if:- The ceramic base cracks during installation.
- The wire harness cannot be kept clear of the burner flame area.
- The mounting point is loose, rusted through, or no longer holds the igniter securely.
Step 5: Reassemble and restore power
- Reinstall the burner access panel or door switch panel fully so the furnace can run normally.
- Open the gas shutoff valve again if you closed it earlier.
- Turn the furnace power back on at the switch or breaker.
- Set the thermostat to call for heat and stay near the furnace for the startup.
If it works: The furnace is reassembled, powered, and ready for a live test.
If it doesn’t: If the furnace does not respond at all, check that the panel is seated correctly, the door switch is engaged, and the breaker or service switch is on.
Stop if:- You smell gas after reopening the valve.
- The access panel will not seat correctly or leaves wiring exposed.
Step 6: Verify the new igniter fixed the heating cycle
- Watch the startup sequence. The inducer should start first, then the igniter should glow or spark depending on furnace design, and the burners should light smoothly.
- Let the furnace run for several minutes and confirm the main blower starts and warm air reaches the registers.
- Listen for normal operation without repeated clicking, short cycling, or burner dropout.
- Check again after one more heat call later the same day to make sure the repair holds in real use.
If it works: The burners light reliably, the furnace completes a normal heat cycle, and warm air is delivered consistently.
If it doesn’t: If the new igniter does not glow, the burners still do not light, or the furnace shuts down again, the problem may be the flame sensor, pressure switch, control board, gas supply, or wiring and needs further diagnosis.
Stop if:- The furnace lights with a bang, delayed ignition, or rolling flame.
- The breaker trips, wires overheat, or you see sparking.
- The furnace repeatedly tries to light and then locks out.
Replacement Parts
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FAQ
How do I know if my furnace igniter is bad?
A bad igniter often shows up when the furnace starts its draft fan but the burners never light. Sometimes the igniter is visibly cracked. On hot surface igniters, you may also notice that it never glows during startup.
Can I replace a furnace igniter myself?
Many homeowners can replace one if the igniter is easy to access and the replacement is an exact match. The job is usually straightforward, but you should stop if you smell gas, find burned wiring, or are unsure about the diagnosis.
Do I need to shut off the gas to replace the igniter?
You should always shut off electrical power first. Closing the nearby gas valve is a sensible extra precaution if it is easy to identify and operate, especially since you are working in the burner area.
Why should I avoid touching the igniter element?
The element is fragile, and oils or pressure from your fingers can shorten its life or damage it. Handle the part by the ceramic base or mounting bracket whenever possible.
What if the new igniter does not fix the furnace?
If the furnace still will not light, the root cause may be elsewhere. Common next checks include the flame sensor, pressure switch, control board, wiring, or gas supply. At that point, more diagnosis is usually needed.