C-10, A/C Clutch Circuit Diagnosis: Description

When A/C is selected a 12-volt signal is supplied to A/C request input of PCM. A/C compressor clutch relay is controlled through PCM. PCM monitors A/C refrigerant pressure. If A/C refrigerant pressure, and engine operating conditions are within a specific calibrated acceptable range, PCM will enable A/C compressor relay. This is done by providing a ground path for A/C relay coil within PCM. When A/C compressor relay is enabled, battery voltage is supplied to compressor clutch coil.

PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless throttle is greater than 90 percent, A/C head pressure is greater than 414 psi (29.1 kg/cm² ) or 4.27 volts, or less than 34 psi (2.3 kg/cm² ), or .35 volt as determined by A/C refrigerant pressure sensor, ignition voltage less than 10.5 volts, engine speed greater than 4500 RPM for 5 seconds, engine coolant temperature greater than 257°F (125°C), and intake air temperature less than 41°F (5°C).