Lennox Furnace LED on (solid) error code
The red LED stays lit continuously without flashing. On this control, a solid LED means the board has an internal fault and must be replaced.
Also shown as: solid red LED, LED stuck on, continuous on, steady red light
Last updated: September 30, 2026
What causes the LED on (solid) error?
- Failed ignition control board
How to fix Lennox LED on (solid) — step by step
Work through these in order, from simplest and safest first. Stop as soon as the code clears.
- Power-cycle once
Turn the furnace off at the service switch for 60 seconds and back on. If the LED returns to flashing normally, the board recovered. - Call a technician for board replacement
A persistently solid LED means the board's self-check failed. Replacing a control board requires transferring wiring and configuration — a professional job.Safety warning: Turn power off at the breaker before the control compartment is opened. Never handle a control board with power applied.
When to call a technician
- The LED stays solid after a power cycle
Frequently asked questions
Can a solid LED ever be normal?
No. Normal states are a slow or fast heartbeat pulse, or flashing fault codes — never a continuous glow.
Is the furnace safe with a failed board?
The board has shut the furnace down, so it will not run. Leave it off until the board is replaced.
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.