Normal Operation

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Under normal operation, when A/C is requested, a message is sent over the bus from the HVAC module to the PCM. The PCM receives input from the A/C cycling switch through circuit 883 (PK/LB). Voltage is provided to the A/C cycling switch through circuit 1040 (RD/BK)/348 (VT).

The PCM provides a ground for the A/C clutch relay coil through circuit 73 (OG/LB). The A/C clutch relay coil receives ignition voltage through circuit 391 (RD/YE). Ignition voltage for the A/C clutch relay switch is provided through circuit 1810 (LG/OG). When the relay is activated, ignition 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:

Fuse(s)
Wiring, terminals or connectors
A/C pressure transducer
PCM
A/C control relay
HVAC module
A/C cycling switch
A/C compressor clutch field coil
A/C clutch air gap