Pinpoint Test B : P0645, P0646, P0647: Notes
WARNING: This page is about a different car, the 2018 Ford F-550 Super Duty, 2018 Ford F-450 Super Duty, 2018 Ford F-350 Super Duty, and 2018 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
Refer to Manual Climate Control System for schematic and connector information.
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. |
| P0646 | A/C Clutch Relay Control Circuit Low | This DTC sets when the relay circuit is off and ground 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. |
| P0647 | A/C Clutch Relay Control Circuit High | This DTC sets when the PCM grounds the relay circuit and excessive current draw (short to voltage) is detected on the relay circuit. |
Possible Sources
- Wiring, terminals or connectors
- A/C clutch relay
- PCM
Visual Inspection and Diagnostic Pre-checks
- Inspect BJB fuses 3 (20A) and 16 (10A).