The Climate Control Unit (CCU) in the Porsche 993 has the following functions:
- Monitor the air temperature in the cabin by blowing air over a sensor in the CCU front panel (CCU fan)
- Monitor the CCU fan operation
- Monitor the ambient (outside) air temperature
- Monitor the oil temperature
- Monitor any freezing of the A/C evaporator
- Monitor both front fans and rear fan operation (fault detection)
- Monitor the air temperature in the two front and mixer chambers (vent air temperature)
- Monitor the engine temperature to be able to run the aux fan in cooling mode at ignition off if needed
- Control the A/C condenser fan low-speed setting. (high speed controlled by pressure switch)
- Control the oil cooler fan in the right front fender (low and high speed)
- Control the front interior fan speed (two fans, 4 steps using PWM)
- Control the engine compartment (rear) cooling/hot air blower fan (low and high speed)
- Control the amount of fresh air from the front air intake (servo motor)
- Control the amount of heated air from the engine heat exchangers (two mixer servo motors, one for each side of the dashboard)
- Control the amount of air to the defroster or center vents (servo motor)
- Control the amount of air to the footwell vents (servo motor)
- Control the recirculation vacuum actuator behind the CCU on late 1995 and forward cars.
- Control the A/C compressor clutch mechanism
- Monitor the gear shift, if reverse gear is selected, both mixer valves close to avoid exhaust fumes in the cabin
- Activate the DME Coasting Shutoff function in the engine control unit
- Log any faults detected in the systems and present them through the OBD interface
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