Error code reference

Lennox Heat Pump Error Code Green OFF / Red SLOW Flash

Low pressure fault

Low pressure fault — compressor cycled off due to low pressure switch trip.

First step from the service manual

Remove any blockages or restrictions from coils and/or fans. Check indoor and outdoor fan motor for proper current draws.

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

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Green OFF / Red SLOW Flash on my Lennox Heat Pump

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Low pressure fault — compressor cycled off due

From Service Manual 186749, p.41:

1.Remove any blockages or restrictions from coils and/or fans. Check indoor and outdoor fan motor for proper current draws.

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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