Compressor

Compressor

The Cayenne is equipped with a swash plate (regulated) compressor controlled on the low side that is similar to a compressor in a sports car. The refrigerant has a pressure of 10-30 bar after exiting the compressor at a temperature of about 100 degrees C. The compressor runs whenever the engine runs.







If the temperature of the refrigerant is 118 degrees C the DME will request the climate control module to shut down the AC system.

Through an electronic control valve integrated into the compressor the low side pressure in the compressor controls the swash plate. The control valve is triggered by a PWM signal from the Climate Control module. The control valve is operated depending on the signal of the evaporator temperature sensor.
The basis frequency for the valve is 400 Hz.

Changeable PWM Signal (400 Hz)

Electricity Strength (Ampere) Compressor Status

0.0 - 0.3 Off (no burden)
0.3 - 0.8 Continuous adjustment
>0.8 Regulated

The piston stroke can be continuously varied. A large stroke for large refrigerant capacity and a smaller stroke for smaller capacity.

Because the compressor works with a variable capacity there is no compressor relay. This means that the compressor is always turning but there is no output at the lowest portion of the compressor stroke.

The AC compressor is turned off at external temperatures of under about 2 degrees C (35 degrees F) and cannot be turned on manually or by pushing the Auto button.

If the system pressure is critical at about 40 ±4 bar the over pressure valve is opened in order to protect the system from damage. After the pressure is regulated. the valve closes. The valve can be found on the left of the compressor next to the wiring on the high pressure side.

Pressure Damper







The pressure damper decreases noise. It is a simple cylinder that is built into the low pressure side between the expansion valve and the compressor.
It is used to keep the noise of the compressor from being heard in the passenger area. The damper is in front of the left wheel housing cover.

Condenser







The condenser is integrated into the radiator module (sandwich design).
The following diagram shows the connecting flange to the condenser.







The vertical direction of the condenser lines cools the entrance temperature from 100 degrees Cto about 60 degrees C. In order to make this jump in temperature possible at any time, the smaller engine fan is triggered (see the diagram in section DME, Cooling Fans). The following triggering of the cooling fans is possible, depending on the pressure of the AC system.







Drier Cartridge







The replaceable drier cartridge is in a special line. This receptacle line is integrated into the right side of the condenser (see section "Condenser").

To change the drier cartridge, the refrigerant system must he discharged. After the rubber cover is removed, the safety ring can be removed. With a special tool out of the Porsche "slide hammer pulling kit", the sealing covers can be pulled up and removed.







After the covers have been removed, the drying cartridge can be pulled out with the spacer stick. The cartridge unit is approximately 380 mm long. It is composed of a spacer and a sleeve with a netted insert that contains a moisture binding material. Until saturated, the drying cartridge can chemically bind 612 grams of system.







The drying cartridge does not have a set maintenance time frame.

Expansion Valve (front)

The main function of the expansion valve is to keep the pressure of the liquid refrigerant down to 1 - 3 bar. The valve is built in as a classical H configuration with a membrane case on the upper side and can be used to change the volume of the refrigerant that is allowed to flow back to the compressor.







The pressure sensor shown in the diagram is described in section "Pressure Sensor Climate Control".

Evaporator (front)

The evaporator can be found in the middle of the air distribution housing. The design is similar to that of the condenser. The evaporator will remove heat from the air. This will condense the humidity on the damper. This condensed system will then be directed through a run-off hose. The evaporator temperature sensor is positioned in the air distribution housing right behind the evaporator (see section "Evaporator Temperature Sensor").

System Overview/Block Diagram (2 Zone Climate Control)







The block diagram below shows the most important actuators and sensors that are used for controlling the automatic Climate Control.