Lennox ML193UHE furnace 12 red flashes: Unexpected Flame
Safety issue — act now
What do 12 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03? The control sensed flame while the gas valve was not energized. Flame should not be present then, so this is a safety condition, not a routine fault.
This condition involves the gas or combustion side. If you smell gas or a CO alarm sounds: leave, then call your gas utility. Diagnostic info here is reference — combustion repairs are for licensed technicians. All six emergency signs →
Unexpected flame calls for gas-valve and flame-proving diagnosis by a qualified technician. No homeowner restart, gas-valve work or reset attempt is appropriate while the cause is unknown.
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 do 12 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03?
The control sensed flame while the gas valve was not energized. Flame should not be present then, so this is a safety condition, not a routine fault.
How do I fix Lennox ML193UHE furnace 12 red flashes?
If you smell gas or a CO alarm is sounding, leave right away, do not touch electrical switches, and call the gas utility or 911 from outside. With no such signs, keep the furnace off, make no restart attempts, and call a technician promptly.
How much does it cost to fix Lennox ML193UHE furnace 12 red flashes?
Expect diagnosis of the gas valve and flame-proving circuit. Whether parts are needed depends on what is found; the code alone does not name a failed component.
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
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These codes use the same lennox ml193uhe with ignition control 103217-03 system.