Refrigerant Circuit

1 Solenoid clutch
2 Compressor
3 Condenser
4 Drier
6 Safety switches (high/low-pressure pressostats)
7 Expansion valve
8 Evaporator
9 Temperature switch
10 High-pressure gas
11 High-pressure liquid
12 Low-pressure liquid
13 Low-pressure gas

After switching on air-conditioning system, the refrigerant circuit is activated, i.e. the solenoid clutch receives current. This produces a positive connection between belt pulley and armature clutch plate and the compressor is driven.

The compressor, a major component of the system, increases the pressure of refrigerant vapors. Refrigerant vapors are drawn in on the intake side of the compressor. the refrigerant is compressed, whereby the vapor temperature rises. the high-pressure vapors pass via a high pressure pipe to a condenser located on the face of the engine radiator. the hot refrigerant is cooled off by wind from driving and an additional fan. Refrigerant vapors condense and turn into liquid when reaching the dew point temperature. the high pressurized refrigerant is delivered to the drier. the turn drier flask extracts particles of dirt, humidity and even acid from the refrigerant but only to the extent of approx. 6..10 grammes in R12 systems and 10...16 grammes in R 134a systems.

Refrigerant continues on to the expansion valve from the drier. the expansion valve makes up a point of separation in the system. the expansion valve meters the refrigerant. the volume of refrigerant is controlled by the temperature and presure at the outlet of the evaporator. the refrigerant evaporates and cools off considerably in the evaporator. Fresh air-or more precisely circulated air-flowing past the cold evaporator, with blower support, is cooled accordingly and delivered into the passenger compartment via nozzles.

The evaporated refrigerant is drawn in again by the compressor, whereby the refrigerant circuit is completed.

Moisture from the fresh or circulated air, flowing past the evaporator, condenses on the cold fins. the condensation on the evaporator is discharged outdoors via rubber hoses on the transmission tunnel and could cause a puddle of up to 200 ml underneath a parked car depending on the atmospheric moisture. This is completely normal and does not indicate a leak.

If could happen that the condensation water freezes on the fins of the evaporator. An evaporator temperature sensor prevents the formation of ice in that it switches the compressor oft at 2 °C. the compressor is switched on again with a reversing range of 2 °C. A safety switch (high or low-pressure pressostat) switches the air-conditioning system oft when pressure is too high or too low. This prevents damage to the air-conditioning system. A medium-pressure pressostat switches the second stage of an additional fan on at a pressure of about 18 bar.

In this way the compressor is not switched off and on so often, as the maximum high pressure is not reached so fast.