Error code reference

Lennox Air Conditioner Error Code E427

The inverter has detected a DC peak fault condition (55A or higher), causing compressor and fan to stop…

The inverter has detected a DC peak fault condition (55A or higher), causing compressor and fan to stop (inverter code 21).

First step from the service manual

Check for high pressure, condenser fan failure, locked compressor rotor or overcharge. Disconnect power to outdoor unit and restart.

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

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E427 on my Lennox Air Conditioner

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The inverter has detected a DC peak fault

From Service Manual 873192, p.44:

1.Check for high pressure, condenser fan failure, locked compressor rotor or overcharge. Disconnect power to outdoor unit and restart.

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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