Rheem Furnace Igniter Not Working - Causes & Fix

Rheem Furnace Igniter Not Working — What’s Happening

When a Rheem furnace igniter is not working, the furnace fails to complete its ignition sequence. The igniter may never heat up or glow, or it might heat but the burners never light and the control board aborts the call for heat. This is a symptom rather than a single fault code. Rheem troubleshooting guides point to the full ignition chain, including control board issues, rollout switch trips, flame sensor problems, gas valve operation, and manifold pressure conditions, not just the igniter alone.

Rheem furnaces use either a hot surface igniter or a spark igniter. Both types can fail to work because of a bad igniter element, loose wiring, control board faults, interrupted gas supply, or safety switches that prevent the sequence from starting. Homeowners often see no heat and assume the igniter is bad, but the real cause can be upstream or downstream in the ignition process.

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Most Likely Causes

• Failed igniter element A hot surface igniter can crack or burn out and test open or infinite ohms, which is a direct igniter failure and the most common cause.
• Loose or disconnected igniter wiring The igniter wire runs through the frame to the control board, and an open connection or corroded plug will prevent the igniter from receiving power.
• Dirty flame sensor or flame-proving failure A dirty or failed flame sensor will cause the furnace to shut down right after ignition or prevent the gas valve from staying open, which looks like an igniter problem to the homeowner.
• Gas supply or gas valve issue If the gas cock is off or the gas valve does not open, the igniter will glow but the burners will not light and the sequence will abort.
• Tripped rollout switch or control lockout Rheem lists manual reset rollout switch trips and soft lockout conditions as causes of ignition failure, both of which must be cleared before the igniter will work.
• Control board or power fault Control board issues, twinning faults, or a loss of 115 V power can prevent the ignition sequence from starting at all.
• Open door safety switch or airflow restriction An improperly seated access panel, clogged filter, or blocked condensate line can interrupt the safety circuit and stop ignition before the igniter ever fires.

How to Diagnose and Fix

1. Verify the thermostat is calling for heat and confirm that the furnace has power at the service switch and breaker.
2. Check that the access panel or blower door is fully seated so the door safety switch is closed and the control circuit is enabled.
3. Identify whether your Rheem furnace uses a hot surface igniter or a spark igniter by inspecting the burner compartment.
4. Observe the ignition sequence and note whether the igniter glows or sparks, whether the gas valve clicks, and whether the burners light.
5. Test the hot surface igniter with a multimeter at the igniter leads (disconnect power first). An open or infinite reading means the igniter has failed and must be replaced.
6. If the igniter glows but the burners do not light, verify the gas cock is open and gas is supplied to the furnace, then check for a failed gas valve or tripped rollout switch.
7. Inspect the flame sensor rod for heavy soot or corrosion and clean it with fine sandpaper if the burners light briefly then shut off.
8. Check for a soft lockout condition by turning off power to the furnace for one minute, then restore power and try a new call for heat. If the fault persists, inspect the control board and wiring for damage or loose connections.

Parts You Might Need

Related Error Codes

If your appliance also shows a code on the display, these match this problem:

• Rheem Furnace 2 Flashes error code
• Rheem Furnace 3 Flashes error code
• Rheem Furnace 4 Flashes error code

When to Call a Pro

Call a qualified HVAC technician if you are not comfortable working with gas appliances, if testing the igniter requires disassembly you are unsure about, or if basic checks do not isolate the fault. Gas valve replacement, control board diagnosis, manifold pressure testing, and rollout switch investigation all require proper tools and training. A technician can also verify correct combustion, check for carbon monoxide hazards, and reset or replace components that require gas line work or electrical troubleshooting beyond the igniter itself. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.