7 FLASHES
York
Low Flame Sense / Flame Sense Lockout
Furnace will not start heating cycle; LED shows 7 flashes on York control board.
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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
Weak flame signal due to dirty sensor, Poor burner grounding, Incorrect orifice size or low input, Faulty control board flame circuit
How to Fix / Troubleshooting
Safety: Turn off power before removing the burner door. Avoid touching hot components.
- Clean and reposition flame sensor: Remove the flame sensor, clean with fine abrasive pad, and reinstall so it is fully engulfed in the burner flame when operating.
- Check burner and manifold: Inspect burners for rust, debris, or misalignment. Clean burner ports with a soft brush and compressed air (outdoors). Ensure burners are seated correctly in the manifold.
- Verify ground: Confirm that the furnace has a solid ground connection to the electrical panel. Tighten ground screws on the control board and burner assembly.
- Reset lockout: Turn power off for 30 seconds, then back on. Call for heat and observe. If the 7-flash returns after several attempts, the board may not be reading flame current correctly.
- Professional diagnosis: A technician can measure flame rectification current in microamps and determine if the board or sensor circuit is faulty.
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Repair Difficulty
Hard
4/5
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