Lennox ML193UHE furnace red LED off: No Power or Board Fault
Professional repair
What does it mean when the red LED is off on a Lennox ML193UHE with ignition control 103217-03? A dark LED means the control has no power or has detected a board fault. It does not say which of the two applies.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Safe checks before calling
Check that the thermostat display is on, the furnace's external service switch is in the on position, and the access panel is seated. Do not reset a tripped breaker; report it to a technician.
If external power looks normal, a technician should check control power, fuses and the board. Live-board testing and fuse replacement are not homeowner tasks.
Possible causes
- Furnace power interrupted at the external switch or breaker DIY-CHECKABLE
- Board fault detected by the ignition control TECH
Parts for this code
No model-verified part number is listed here. Have the fault diagnosed and the correct part matched to your furnace before ordering.
Questions about this code
What does it mean when the red LED is off on a Lennox ML193UHE with ignition control 103217-03?
A dark LED means the control has no power or has detected a board fault. It does not say which of the two applies.
How do I fix Lennox ML193UHE furnace red LED off?
Report what you found at the thermostat, service switch, breaker and access panel. A technician then traces control power through the circuit and fuse before deciding the board is at fault; a dark LED alone does not justify a new board.
How much does it cost to fix Lennox ML193UHE furnace red LED off?
If power was simply interrupted, there may be no repair. Otherwise the bill depends on diagnosis time and whether a fuse, wiring or a replacement control board is required.
Applies to
ML193UHE
Different Lennox generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Lennox ML193UHE Installation Instructions, p.39
Verified against Lennox ML193UHE Unit Information / Service Literature, p.9
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
Related Lennox furnace codes
These codes use the same lennox ml193uhe with ignition control 103217-03 system.