A/C Request Signal Circuit Diagnosis

Turning on A/C system supplies battery voltage to A/C compressor clutch and Powertrain Control Module (PCM) terminal E12 through circuit No. 59, increasing idle speed. PCM does not control A/C compressor clutch. If A/C compressor clutch is malfunctioning, repair basic A/C system problem. If A/C system is operating properly and idle speed drops too low when A/C compressor turns on or flares too high when A/C compressor turns off, check for an open circuit No. 59 to PCM. If circuit is okay, repair faulty PCM connection (terminal E12) or replace faulty PCM.

Fig 1: A/C Clutch Circuit Schematic - 5.7L VIN K ("C" & "K" Series) A/C Request Signal Circuit Diagnosis

Fig 2: A/C Clutch Circuit Schematic - 5.7L VIN K ("G" Series) A/C Request Signal Circuit Diagnosis

Fig 3: A/C Clutch Circuit Schematic - 5.7L VIN K ("L" & "M" Series) A/C Request Signal Circuit Diagnosis

Fig 4: A/C Clutch Circuit Schematic - 5.7L VIN K ("P" Series) A/C Request Signal Circuit Diagnosis