| Description and Operation The air conditioning system is controlled by an thermostatic expansion valve. R134a refrigerant is used. There are three different variants available: - Front air conditioning system with manual temperature control
- Front air conditioning system with automatic temperature control (Climatronic)
- Front and rear air conditioning system with automatic temperature control (Climatronic)
Depending on the engine variant, two different air conditioning compressors are used: - Constant-displacement Ford FS10 compressor for vehicles with 2.0L DOHC and 2.3L DOHC engine built up to 08/2002
- Variable-displacement Sanden SD7V16 compressor for vehicles with 2.0L DOHC and 2.3L DOHC engine built 08/2002 onwards
- Variable-displacement Sanden SD7V16 compressor for vehicles with 1.9L TDI diesel engine and the 2.8L VR6 engine
In order to prevent icing up of the evaporator core, all vehicles built up to 11/2001 except vehicles with 2.8L or 1.9L Diesel engine with automatic temperature control (ATC) are equipped with an de-icing switch on the evaporator core. This switch measures the surface temperature of the evaporator cooling fins using a thermo switch. If the measured temperature drops below about +1°C, the de-icing switch disengages the A/C compressor clutch. When the temperature rises above +2.5°C, the A/C compressor is switched on again. The advantage of the Sanden compressor is that it does not cut in abruptly during control (except when first switched on). Due to the variable piston stroke, the pressure is constantly regulated, which means that the compressor is always running in normal operation. The piston stroke is driven by the variable swash plate and controlled by the ratio of high pressure to low pressure. When switched on, the compressor delivery starts with 40% and varies between 5% and 100% when running. Then the pressure on the low pressure side remains at a constant value. Refrigerant Circuit | Item | Description | | 1 | Condenser core | | 2 | Air conditioning (A/C) compressor | | 3 | Muffler | | 4 | Blower motor | | 5 | Evaporator core | | 6 | Thermostatic expansion valve | | 7 | Receiver/drier | | 8 | Condenser fan motor | | 9 | High-pressure (gaseous and hot) | | 10 | High-pressure (liquid and warm) | | 11 | Low-pressure (liquid and cool) | | 12 | Low-pressure (gaseous and cool) | Function The A/C compressor (2) is driven by the engine and primes the gaseous refrigerant out of the muffler (3) and compresses it. The refrigerant heats up to a temperature between 70°C and 110°C and is passed to the condenser core (1) under high-pressure. At this point heat is drawn from the refrigerant by the air being forced past the cooling fins. Because of this heat loss, the refrigerant liquifies and leaves the condenser core. The refrigerant reaches the receiver/drier (7) under high-pressure, which filters out the moisture absorbed by the refrigerant and is also used as a reservoir. The thermostatic expansion valve (6) regulates the amount of liquid refrigerant passed to the evaporator core (5) according to the pressure and temperature in the evaporator core. In the evaporator core the liquid refrigerant converts back into the gaseous state and this causes heat to be extracted from the air coming into the vehicle. The air therefore cools down and the moisture it contained is given up at the evaporator core. The gaseous refrigerant stream, coming from the evaporator core under low-pressure, enters the upper bore of the expansion valve and is sucked up again over the muffler by the A/C compressor. The system is protected by the 3-way pressure switch, in order to prevent damage by excessive pressure (example, because of overfilling). If the pressure exceeds the maximum allowed, the 3-way pressure switch turns off the A/C compressor. On vehicles with 1.9L TDI engine with 96kW (130PS), the 3-way pressure switch is replaced by the A/C pressure transducer sensor which sends a pulse width modulation signal to the A/C clutch module and to the powertrain control module (PCM). The A/C clutch module engages and disengages the A/C clutch after evaluation of the different input signals. These signals come from the heater blower switch via the outside temperature thermo switch (vehicles with manual temperature control) or the automatic temperature control module (vehicles with automatic temperature control), the A/C pressure transducer sensor and the PCM. Air conditioning components | Item | Description | | 1 | Thermostatic expansion valve | | 2 | Evaporator core | | 3 | Condenser core | | 4 | Air conditioning (A/C) compressor | | 5 | Receiver/drier | | 6 | Muffler | | 7 | High-pressure cutoff switch | | 
