Symptoms
- Blower runs but burners never light
- No pilot light to check; furnace uses an electronic igniter
- Furnace may try to start, click, then lock out
Likely causes
- CommonCracked or burned-out hot-surface igniterThese fragile ceramic elements wear out after years of heating and cooling cycles.
- CommonDirty flame sensor causing lockout after ignitionSometimes the igniter works fine but the furnace shuts down right after, mimicking an ignition failure.
- PossibleFailed igniter control relay or control boardElectrical components send power to the igniter and can fail with age.
- PossibleBlocked gas valve or closed shutoffNo fuel means no flame even with a working igniter.
- PossibleFurnace in soft lockout after multiple failed attemptsMany furnaces lock out for safety after 3+ failed ignition tries and need a reset.
What to do
- Turn the furnace off at the thermostat and the power switch, then wait one minute.
- Turn power back on and watch a full cycle; you may see a faint orange glow at the igniter through a viewing port.
- Confirm the gas valve at the furnace is open and any propane tank has fuel.
- Check the breaker hasn't tripped and the furnace door switch is fully engaged.
- If you see the igniter glow but no flame appears, the gas valve or orifice may be at fault.
- If you see no glow at all, the igniter itself has likely failed and needs replacement.
- Don't attempt to test or replace the igniter with power connected; this is best left to a technician unless you're experienced.
Tools and parts
- Flashlight
Hot-surface furnace igniterSearch: “furnace hot surface igniter replacement model”
When to call a pro
Call an HVAC technician to test and replace the igniter or control board if it doesn't glow after a power reset.
Safety
Use caution
Disconnect power before inspecting or touching igniter wiring, and never touch a hot-surface igniter directly, even when it appears off, until it has fully cooled.