Manual Climate Controls

DESCRIPTION

The Compressor for the air conditioning system is belt-driven by the engine through the A/C Compressor Clutch. The Clutch allows the Compressor to be disengaged when air conditioning is not required or to remove the air conditioning load from the engine when needed.

OPERATION

Operation of the Compressor depends on the particular A/C Mode selected. When the A/C Mode Selector Switch is in MAX, LOWER, NORM, VENT, DEFOG or DEF, battery voltage is applied through Instrument Panel (I/P) Fuse Block Fuse 17 and the Heater and A/C Control Assembly Mode Selector Switch to the Powertrain Control Module (PCM).

The current path to the PCM is through the Pressure Cycling Switch and the A/C High Pressure Cut-Out Switch, which are normally closed. The Pressure Cycling Switch opens if the refrigerant pressure drops low enough that freezing of the evaporator may take place (175 kPa/25 psi). It closes again when the refrigerant pressure rises enough that additional cooling is required. In this way the A/C Compressor is cycled on and off to maintain a low temperature in the evaporator without allowing condensation to freeze.

The A/C High Pressure Cut-Out Switch is normally closed. When refrigerant pressure becomes too high for normal operation., the A/C High Pressure Cut-Out Switch opens, signaling the PCM to disengage the A/C Compressor Clutch.

The A/C Compressor Control Relay is operated by the PCM. When the PCM receives the A/C ON signal, the PCM grounds the A/C Compressor Control Relay energizing the Relay. When the Relay is energized, voltage is applied to the A/C Compressor Clutch through the closed contacts of the Relay.

If the PCM determines that the engine load should be reduced, such as during full throttle, the PCM de-energizes the A/C Cut-Out Relay which removes voltage from the A/C Compressor Clutch, thus removing the A/C load from the engine.

The Compressor Clutch Diode connected across the A/C Compressor Clutch provides a path for the current resulting from voltage spikes. The voltage spikes are generated by the collapsing magnetic field of the clutch coil each time the clutch is de-energized.