Error code reference

Carrier Hvac Error Code 45

Control board has failed internal start-up tests and must be replaced.

First step from the service manual

Replace the fan coil control board. No other service procedure will correct.

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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Control board has failed internal start-up

From Service Manual 761143, p.35:

1.Replace the fan coil control board. No other service procedure will correct.

2.Measure control board supply voltage at the test points. Expected: 12 VDC and 5 VDC; a drop below 4.75 VDC on the logic rail points to a failed onboard regulator.

3.Inspect all connectors on the main control for corrosion, thermal stress, or backed-out pins. Reseat each connector with the power disconnected.

Part WPW10804018

Electronic control board

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First step from the service manual

Get the full diagnostic procedure for 45.

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