Model reference

Lennox G27M4(X)100

Furnace

1 document12 error codes

Available documentation

Service Manual

G27M Service Literature28 pg
Covers this model

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LED1-ALT_FAST_FLASH/LED2-ALT_FAST_FLASH on my Lennox G27M4(X)100

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Improper main ground or line voltage

From Service Manual 863309, p.41:

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-ALT_FAST_FLASH/LED2-ALT_FAST_FLASHImproper main ground or line voltage below 75 volts; OR broken ignitor; OR open…LED1-ALT_SLOW_FLASH/LED2-ALT_SLOW_FLASHWatchguard LED1-FAST_FLASH/LED2-FAST_FLASHNormal operation LED1-FAST_FLASH/LED2-SLOW_FLASHMain power polarity reversed LED1-OFF/LED2-ONCircuit board failure or control wired incorrectly.LED1-OFF/LED2-SLOW_FLASHPressure switch open or has opened 5 times during a single call for heat; OR…LED1-ON/LED2-ONCircuit board failure or control wired incorrectly.LED1-ON/LED2-SLOW_FLASHRollout switch open OR 9-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 open. Units with board 63K8901 or 24L85 LED1-SLOW_FLASH/LED2-SLOW_FLASHPower on

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