4.6L and 5.4L only

WARNING: This page is about a different car, the 2009 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

Voltage is provided to the A/C cycling switch through circuit 391 (RD/YE). If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the dual-function pressure switch (4.6L and 5.4L) through circuit 198 (DG/OG). If the dual-function pressure switch (4.6L and 5.4L) is closed (pressure not excessive), voltage is sent to the PCM through circuit 420 (DB/YE). When the PCM receives voltage from the pressure switches, the PCM provides a ground for the A/C clutch relay through circuit 321 (GY/WH).

When the relay is activated, ignition voltage is supplied to the A/C clutch solenoid through circuit 883 (PK/LB). Ground is supplied for the A/C clutch through circuit 1205 (BK).

DTC B2175 A/C Request Signal Circuit Short to Ground - The module senses a continuous short to ground on the A/C request circuit.

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
PCM
SJB
HVAC module
A/C cycling switch
A/C control relay
A/C clutch air gap