Controls and Compressor Operation

When an A/C  request is received by the PCM  , the PCM  engages the A/C  clutch relay when all of the following conditions are met:

• The PCM  does not detect excessively high or low refrigerant pressure from the A/C  pressure transducer.
• The PCM  does not detect an ambient air temperature below approximately 35.6°F (2°C).
• The PCM  does not receive a message from the FCIM  detecting an evaporator temperature below approximately 35.6°F (2°C).

The PCM  monitors the discharge pressure measured by the A/C  pressure transducer. The PCM  interrupts A/C compressor operation in the event the A/C  pressure transducer indicates high system discharge pressures. It is also used to sense low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM  does not allow the A/C  clutch to engage.

The FCIM  adjusts the air inlet door depending on the humidity measured by the in-vehicle temperature and humidity sensor. If the vehicle cabin becomes too humid and recirculated air is selected, the FCIM  adjusts the air inlet door to allow more fresh air. When the humidity level drops, it may adjust back to partial recirculated air. The FCIM  also adjusts the system based on in-vehicle temperature.