Normal Operation

WARNING: This page is about a different car, the 2008 Ford RV Cutaway, 2008 Ford Econoline, 2008 Ford E450 Super Duty, and 2008 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

Under normal operation, voltage is provided to the function selector switch through circuit 498 (PK/BK). When A/C is requested, voltage is sent from the function selector switch to the A/C cycling switch through circuit 348 (VT). Voltage is sent from the A/C cycling switch to the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) through circuit 441 (RD/YE). Voltage is sent from the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) to the PCM through circuit 347 (BK/YE).

The PCM provides a ground for the A/C clutch relay coil through circuit 331 (PK/YE). The A/C clutch relay coil receives ignition voltage through circuit 361 (RD). Battery voltage for the A/C clutch relay switch is provided through circuit 932 (GY/WH). When the relay is energized, voltage is supplied to the A/C clutch solenoid through circuit 321 (GY/WH). Ground is supplied for the A/C clutch through circuit 57 (BK).

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
PCM
Function selector switch
A/C control relay
A/C clutch air gap