Error code reference

Lennox Air Conditioner Error Code E428

The inverter has detected a high main input current condition (inverter code 22).

The inverter has detected a high main input current condition (inverter code 22).

First step from the service manual

Check for high pressure, condenser fan failure 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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E428 on my Lennox Air Conditioner

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The inverter has detected a high main input

From Service Manual 873191, p.43:

1.Check for high pressure, condenser fan failure 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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