E4
Westinghouse
Flame not detected / flame sense failure
Furnace starts inducer and ignitor, gas valve opens briefly, then shuts off with E4; multiple failed ignition attempts.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Dirty or oxidized flame sensor rod, Poor burner ground or loose ground wire, Low gas pressure or partially plugged burner orifices, Defective flame sensor circuit on control board
How to Fix / Troubleshooting
Safety: Shut off power and gas before servicing. Allow burners to cool.
Cleaning and checks:
- Locate the flame sensor on the burner assembly (a small metal rod in front of one burner, connected by a single wire).
- Remove the mounting screw and gently pull out the sensor.
- Clean the metal rod with fine steel wool or a Scotch-Brite pad until shiny. Do not use sandpaper that leaves deep scratches.
- Inspect the sensor wire and connector for corrosion or loose fit at the IFC. Reseat the connector.
- Verify that the burner assembly and furnace chassis have a solid ground connection to the control board (check ground screw tightness).
- Reinstall the sensor, restore power and gas, and test a heat cycle.
If problem persists: Have a technician check gas pressure, burner alignment, and the IFC flame-sense circuit. Do not attempt to adjust gas pressure without proper tools and training.
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Repair Difficulty
Medium
3/5
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