Lennox Furnace LED off error code
The red LED on the ignition control is completely dark. Either the board has no power, or the board itself has failed.
Also shown as: no LED, LED not lit, dark LED, no light on control board
Last updated: September 30, 2026
What causes the LED off error?
- Tripped breaker or furnace service switch off
- Blower compartment door not fully closed (door switch open)
- Blown low-voltage fuse or failed transformer
- Failed ignition control board
How to fix Lennox LED off — step by step
Work through these in order, from simplest and safest first. Stop as soon as the code clears.
- Check power
Make sure the furnace breaker is on and the service switch near the furnace is in the ON position. - Reseat the blower door
Open and firmly close the blower compartment door — its safety switch cuts power when the door is ajar. - Call a technician
If power is good and the LED stays dark, the transformer, fuse, or board needs professional testing.Safety warning: Do not open the electrical compartment yourself. Line voltage inside can cause severe shock — leave panel work to a qualified technician.
When to call a technician
- Breaker and switch are on but the LED stays dark
- The breaker trips again after you reset it
Frequently asked questions
Is a dark LED the same as a fault code?
No — it means the board is not running at all, so it cannot display codes. It is a power problem, not a specific fault.
Could the thermostat cause this?
A dead thermostat cannot cut power to the board's LED. Check the breaker and door switch first.
Sources
Every meaning and fix above was checked against official manufacturer documentation:
FixCode provides general troubleshooting information only — not professional repair advice. If you are unsure about any step, stop and call a qualified technician. Repairs done incorrectly can be dangerous and may void your warranty.