Chart C-10, A/C Compressor Clutch Circuit Diagnosis: Notes

Powertrain Control Module (PCM) delays A/C compressor clutch engagement momentarily after A/C is turned on. This delay allows PCM time to adjust engine RPM before A/C compressor clutch engages. PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: Wide Open Throttle (WOT), high engine RPM, high engine coolant temperature or A/C refrigerant pressure too high or too low.

An A/C refrigerant pressure sensor is used to monitor A/C system pressure. If A/C refrigerant pressure is greater than 429 psi (30.2 kg/cm² ) or less than zero, A/C compressor clutch will not engage. If A/C refrigerant pressure sensor signal wire becomes open, shorted to ground or shorted to voltage, Diagnostic Trouble Code (DTC) 66 will set.

If A/C compressor clutch engages and no refrigerant pressure change is detected, DTC 67 will set. When A/C request is detected by PCM, cooling fan(s) will be turned on unless vehicle speed is too fast.

NOTE: Test numbers refer to numbers on diagnostic chart.

Checks PCM's ability to control A/C compressor clutch relay.
Before replacing A/C system control components, check basic A/C-heater system.
Checks for a grounded circuit No. 459 to Pcm.