Model reference

Lennox G43UF-24B-070

Furnace

1 document12 error codes

Available documentation

Service Manual

G43UF Series Service Literature55 pg
Covers this model

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M+ Max·Lennox Furnace

LED1 ALTERNATING FAST FLASH / LED2 ALTERNATING FAST FLASH on my Lennox G43UF-24B-070

M+

Improper main ground (32M88 during

From Service Manual 537480, p.12:

1.Access service mode to confirm the active fault code and read stored error history.

2.Measure control board supply voltage at test points. Expected: 12 VDC and 5 VDC.

3.Inspect all connectors on the main control for corrosion or backed-out pins.

Part WPW10804018

Electronic control board

Error codes (12)

CodeMeaning

LED1 ALTERNATING FAST FLASH / LED2 ALTERNATING FAST FLASHImproper main ground (32M88 during ignitor warm-up only; 78M47/100973-01…LED1 ALTERNATING SLOW FLASH / LED2 ALTERNATING SLOW FLASHWatchguard LED1 FAST FLASH / LED2 SLOW FLASHMain power polarity reversed LED1 OFF / LED2 ONMain power polarity reversed LED1 OFF / LED2 SLOW FLASHProve switch open, OR blocked inlet/exhaust vent, OR prove switch closed prior…LED1 ON / LED2 ONCircuit board failure or control wired incorrectly.LED1 ON / LED2 SLOW FLASHRollout switch open, OR 12-pin connector improperly attached.LED1 SLOW FLASH / LED2 FAST FLASHLow flame signal LED1 SLOW FLASH / LED2 OFFFlame sensed without gas valve energized.LED1 SLOW FLASH / LED2 ONPrimary or secondary limit switch open SIMULTANEOUS FAST FLASHNormal operation SIMULTANEOUS SLOW FLASHPower on

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