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 A/C compressor clutch coil.

PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless:

• Throttle angle is greater than 90 percent.
• A/C head pressure is greater than 414 psi (29.1 kg/cm² ).
• A/C head pressure is less than 35 psi (2.5 kg/cm² ).
• Ignition voltage is less than 10.5 volts.
• Engine speed is greater than 4500 RPM for 5 seconds.
• Engine coolant temperature is greater than 257°F (125°C).
• Intake air temperature is less than 41°F (5°C).