P0645
Normal Operation and Fault Conditions
Voltage is provided to the A/C clutch relay. When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay.
DTC Fault Trigger Conditions
DTC | Description | Fault Trigger Conditions |
|---|---|---|
P0645 A/C Clutch Relay Control Circuit | This DTC sets when the PCM grounds the relay circuit and more voltage than expected is detected on the relay circuit. This DTC also sets when the relay circuit is off and no voltage is detected on the relay circuit. The PCM expects to detect voltage coming through the relay coil to the relay circuit when it is not grounding it. |
Possible Sources
Wiring, terminals or connectors A/C clutch relay PCM
Visual Inspection and Diagnostic Pre-checks
Inspect BJB fuses 23 (10A) and 42 (15A).
PINPOINT TEST B : P0645
NOTICE: Use the correct probe adapter(s) from the Flex Probe Kit when taking measurements. Failure to use the correct probe adapter(s) may damage the connector.
B1 CHECK THE VOLTAGE TO THE A/C (AIR CONDITIONING) CLUTCH RELAY VOLTAGE SUPPLY CIRCUITS
Ignition OFF. Disconnect A/C clutch relay. Ignition ON. Measure:
Click to display connectors
Positive Lead | Measurement / Action | Negative Lead |
|---|---|---|
A/C clutch relay socket 1 | Ground | |
A/C clutch relay socket 3 | Ground |
Are the voltages greater than 11 volts?
Yes | GO to B2 | |
|---|---|---|
No | VERIFY BJB fuses 23 (10A) and 42 (15A) are OK. If not OK, REFER to the Wiring Diagrams manual to identify the possible causes of the circuit short. If OK, REPAIR the circuit. | |
2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.