34
Carrier
Ignition Proving Failure
Furnace LED shows code 34 (ignition proving failure). Ignitor glows, burners may light briefly then go out.
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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 mispositioned flame sensor, poor burner ground, low gas pressure, partially plugged burners
How to Fix / Troubleshooting
Safety first: Turn off power and gas before removing the burner assembly or flame sensor.
- Clean flame sensor: Remove the flame sensor rod and gently clean it with fine steel wool until shiny. Reinstall so the rod is fully in the burner flame.
- Check burner grounding: Ensure the burner rack is tightly screwed to the furnace chassis and that any green ground wires are secure. Clean off rust at contact points if needed.
- Clean burner ports: If comfortable, remove the burner assembly and use compressed air or a soft brush to clean the burner ports and crossover channels. Do not enlarge the ports.
- Observe flame signal (pro level): A technician can measure microamp flame current. If low, the sensor or control board may need replacement.
If the furnace continues to light and then shut off after a few seconds, call a professional to check gas pressure and combustion safety.
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Repair Difficulty
Hard
4/5
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