A/C Request Signal Diagnosis

A/C Signal Diagnosis:

CIRCUIT DESCRIPTION
Turning "ON" the air conditioning supplies CKT 59 battery voltage to the A/C compressor clutch and to terminal "B12" of the Powertrain Control Module (PCM) to increase and maintain idle speed.
The PCM does not control the A/C compressor clutch. Therefore, if A/C does not function, refer to Heating and Air Conditioning for diagnosis of the system.
If A/C is operating properly and idle speed dips too low when the A/C compressor turns "ON" or flares too high when the A/C compressor turns "OFF," check for an open CKT 59 to the PCM. If circuits are OK, it is a faulty PCM connector terminal "B12" or PCM.