Model reference

Lennox G23Q4/5(X)-75

Furnace

1 document16 error codes

Available documentation

Service Manual

G23(X) Series Service Literature52 pg
Covers this model

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Diagnose your Lennox G23Q4/5(X)-75.

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Test values, resistance specs, and wiring references
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LED Off on my Lennox G23Q4/5(X)-75

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Control failure, power failure, or hard

From Service Manual 789243, p.15:

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

2.Measure door lock assembly resistance across PTC terminals. Expected: ~200 ohms cold.

3.Inspect strike and latch alignment. A misaligned strike prevents the switch stack from closing.

Part W10810403

Door lock assembly

Error codes (16)

CodeMeaning

LED OffControl failure, power failure, or hard lockout on G776 ignition control.LED Slow FlashControl retry period LED Steady OnNormal operation of the G776 ignition control.LED1 Alternating Fast Flash / LED2 Alternating Fast FlashImproper main ground or line voltage below 75 volts; OR broken ignitor; OR open…LED1 Alternating Slow Flash / LED2 Alternating Slow FlashWatchguard LED1 Fast Flash / LED2 Fast Flash (Simultaneous)Normal 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 OffCircuit board failure or control wired incorrectly.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 LED1 Slow Flash / LED2 Slow Flash (Simultaneous)Power on

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