Air conditioning (Operation): Description and operation

Operation

The rear A/C only operates if the front A/C is on to pump refrigerant through the rear evaporator/blower assembly. When the rear A/C switch is selected on, the indicator lamp in the switch illuminates and the rear blower relay is energised. The rear blower relay switches battery power to the blower motor, which runs at the speed selected on the blower speed switch.

The air from the blower passes through the evaporator matrix, which absorbs heat from the air. The cooled air is then supplied to the roof vents through the distribution ducts. The heat absorbed by the refrigerant in the evaporator is sensed by the thermostatic expansion valve. The thermostatic expansion valve then opens and regulates the flow of refrigerant through the evaporator in proportion to the amount of heat being absorbed from the air.

When the rear A/C switch is selected off, the blower stops. The thermostatic expansion valve senses the subsequent decrease in temperature of the refrigerant in the evaporator. The thermostatic expansion valve then closes and stops the flow of refrigerant, except for a minimal bleed flow.