Manual A/C-Heater Systems: Description
A/C-heater system automatically controls vehicle cabin climate for various climate setting combinations available at A/C-heater control panel. A/C-heating system automatically blends cool and warm air in correct proportions to meet cooling/heating settings of A/C-heater control panel. System components include evaporator, compressor, condenser, receiver-drier and expansion valve. See Fig 2.
Compressor operation is protected by an electronic thermostat located on evaporator housing, and by refrigerant pressure switch/pressure sensor located on top of receiver-drier. Electronic thermostat disables compressor clutch when evaporator coil temperature is too low, to prevent evaporator core from icing. Pressure switch/sensor protects compressor and refrigerant system when refrigerant pressure exceeds, or drops below, predetermined levels.
Three different types of pressure switch/sensor are used, depending upon powertrain applications. A dual-pressure switch is used on 3.2L models with Manual Transmission (M/T) and a triple-pressure switch is used on 3.2L models with Automatic Transmission (A/T). On all 3.2L models, pressure switch contacts will open when refrigerant system pressure is too high or too low, opening compressor clutch control circuit. On all 2.2L models, a pressure sensor input to ECM is monitored, and compressor clutch operation is controlled directly by ECM.