55
Carrier
False Flame Sense
Furnace LED shows code 55 (flame sensed with gas valve off). Furnace may shut down and lock 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
Shorted flame sensor to ground, wet or contaminated burner assembly, induced voltage from ignitor, control board fault
How to Fix / Troubleshooting
Safety first: Turn off power and gas. False flame detection can prevent safe operation.
- Inspect flame sensor wiring: Ensure the flame sensor wire is not pinched or touching metal. Replace if insulation is damaged.
- Clean burner area: Remove burner access panel and check for moisture, rust flakes, or debris bridging between burner and sensor. Dry and clean as needed.
- Check ignitor and sensor spacing: Make sure the hot surface ignitor and flame sensor are not touching each other or sharing mounting hardware that could cause feedback.
- Reset control: After corrections, restore power and call for heat. If code 55 persists, the control board may be misreading flame current.
Persistent false flame readings usually require professional diagnosis and possible control board replacement.
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Repair Difficulty
Hard
4/5
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