Error code reference

Carrier Furnace Error Code 45

Control circuitry lockout; auto-reset after one hour due to gas valve relay stuck open, flame sense circuit…

Control circuitry lockout; auto-reset after one hour due to gas valve relay stuck open, flame sense circuit failure, or software check error.

First step from the service manual

Reset power to clear lockout. Replace control if status code repeats.

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

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Control circuitry lockout

From Service Manual 102551, p.43:

1.Reset power to clear lockout. Replace control if status code repeats.

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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