LED_5_FLASH
Lennox
Flame Sensed with Gas Valve Off
Status LED on Lennox furnace control board flashes 5 times; furnace may not start or may shut down unexpectedly.
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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, Strong external flame or pilot source (if present), Faulty control board flame sensing circuit, Miswired burner ground
How to Fix / Troubleshooting
Safety: Turn off power and gas before inspection.
- 1. Inspect flame sensor wiring: Ensure the flame sensor wire is not pinched or touching metal.
- 2. Clean and reseat sensor: Clean the flame sensor and ensure it is properly positioned in the burner flame path.
- 3. Check for external flame: Confirm there is no standing pilot or other flame source near the sensor on models that should be intermittent ignition only.
If the 5-flash code persists, the control board may need replacement.
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Repair Difficulty
Hard
4/5
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