Lennox ML193UHE furnace 5 red flashes: Ignition Watchguard
Professional repair
What do 5 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03? The control reached its maximum number of ignition retries or recycles and entered Watchguard. Lennox service literature describes five total ignition trials followed by a 60-minute Watchguard period before the control tries again.
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 →
Watchguard reports that retries ran out, not why. A technician needs to diagnose the ignition or flame-loss fault behind it; the board's stored code history can help.
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 5 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03?
The control reached its maximum number of ignition retries or recycles and entered Watchguard. Lennox service literature describes five total ignition trials followed by a 60-minute Watchguard period before the control tries again.
How do I fix Lennox ML193UHE furnace 5 red flashes?
Arrange service even if heat returns after the 60-minute period. An automatic retry that succeeds does not prove the cause is fixed. Avoid forcing restarts; let the technician work from the stored codes and the actual ignition sequence.
How much does it cost to fix Lennox ML193UHE furnace 5 red flashes?
Expect charges for diagnosing the ignition or flame-loss cause. Watchguard itself is a control response, so any parts cost depends on what that diagnosis finds.
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
Verified against Lennox ML193UHE Unit Information / Service Literature, p.10
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
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