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Electronic Climate Control
CLIMATE CONTROL SYSTEM
A/C Compressor Controls
Voltage is provided at all times to the A/C compressor clutch relay contacts through fuse 59. With the ignition switch ON (II), voltage is supplied to the relay coil through fuse 3.
With the ignition switch ON (II), the climate control unit grounds the A/C ON input of the PCM through the A/C pressure switch. The PCM then grounds the A/C compressor clutch relay coil. This energizes the coil, which closes the relay contacts and provides voltage through fuse 59 to the A/C compressor clutch. The clutch then engages and begins turning the compressor. By default, when the climate control system is on, the A/C is on.
Evaporator Temperature Sensor
The evaporator temperature sensor is located on the evaporator housing. If the temperature at the evaporator gets too cold, the evaporator temperature sensor sends a signal to the climate control unit to turn off the A/C compressor clutch. This prevents condensation from freezing on the evaporator fins and blocking air delivery into the passenger compartment.
A/C Pressure Switch
The A/C pressure switch is located in the condenser outlet line where refrigerant is in a high temperature/high pressure liquid state. The switch will sense abnormally high or low pressure, and open the circuit. This removes ground from the PCM, and turns off the compressor.