Lennox ML193UHE furnace 3 red flashes: Ignition or Flame Failure
Professional repair
What do 3 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03? During a heat demand, the burners either failed to ignite or the control lost the flame signal after ignition. The same three-flash code covers both events, so it does not tell you which one occurred.
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 →
Ignition, flame proving and the gas system are technician work. A technician can measure flame signal, check gas supply and ignition components, and confirm the burners light and stay lit.
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 3 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03?
During a heat demand, the burners either failed to ignite or the control lost the flame signal after ignition. The same three-flash code covers both events, so it does not tell you which one occurred.
How do I fix Lennox ML193UHE furnace 3 red flashes?
Book a service call and describe what you heard or saw, such as the furnace starting and then stopping. Avoid cycling power or the thermostat to force more ignition attempts; repeated tries do not correct the cause.
How much does it cost to fix Lennox ML193UHE furnace 3 red flashes?
The cost depends on what diagnosis finds in the ignition, flame-sensing or gas supply path. The code alone does not identify a part to replace.
Related symptoms
These symptoms can appear alongside this code. The link is an association, not a diagnosis, and code meanings vary by brand, model and control.
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.