Error code reference

Lennox Air Conditioner Error Code E423

The inverter has detected a circuit problem (inverter code 40).

The inverter has detected a circuit problem (inverter code 40).

First step from the service manual

Disconnect power to outdoor unit and restart. Control locks out after 10 strikes within an hour.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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E423 on my Lennox Air Conditioner

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The inverter has detected a circuit problem

From Service Manual 873196, p.48:

1.Disconnect power to outdoor unit and restart. Control locks out after 10 strikes within an hour.

2.Measure door lock assembly resistance across the PTC terminals. Expected: ~200 ohms cold, rising sharply once energized.

3.Inspect strike and latch alignment. A warped door or misaligned strike prevents the switch stack from closing in the correct sequence.

Part W10810403

Door lock assembly

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