Error code reference

Carrier Hvac Error Code 27

Invalid outdoor unit size

Invalid outdoor unit size — outdoor unit size as provided by User Interface is invalid for the fan coil application.

First step from the service manual

Check communications wiring to be sure User Interface has established communications with outdoor unit or select proper size from valid size list at User Interface.

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

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Step-by-step tests with expected resistance, voltage, and continuity values
Wiring diagram references and connector pinouts from the OEM service manual
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Invalid outdoor unit size — outdoor unit size

From Service Manual 761203, p.15:

1.Check communications wiring to be sure User Interface has established communications with outdoor unit or select proper size from valid size list at User Interface.

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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First step from the service manual

Get the full diagnostic procedure for 27.

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