Automatic air conditioning refrigerant circuit, function

P83.40-3929-79

1 Condenser

2 Fluid reservoir

3 Expansion valve

4 Evaporator

A High pressure, gaseous

B High pressure, liquid

C Low pressure, liquid

D Low pressure, gaseous

A9 Refrigerant compressor

B10/6 Evaporator temperature sensor

B12 Refrigerant pressure sensor

Function requirements, general

 Circuit 61 ON

 Air conditioning switched on

Automatic air conditioning refrigerant circuit, general

Cooling takes place via the automatic air conditioning refrigerant circuit depending on the setting on the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning). The individual components are interconnected through lines and form a closed system.

The automatic air conditioning refrigerant circuit comprises the following subfunctions:

 Function sequence, high-pressure side

 Function sequence, low-pressure side

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Function sequence, high-pressure side

The refrigerant compressor (A9) powered by the engine draws in and compresses the gaseous refrigerant. The refrigerant is heated up intensely in the process. The refrigerant flows through a line into the condenser under high pressure. Here the compression heat is extracted from the extremely hot refrigerant. The refrigerant condenses and changes state from gaseous to liquid.

The compression heat is dissipated via the condenser surface (cooling fins).

The refrigerant flows from the condenser to the fluid reservoir (drier) via a line. When the refrigerant flows through the fluid reservoir it is cleansed of any chemical and mechanical impurities. This protects the downstream components. The cleaned refrigerant flows via a feed line to the expansion valve. The high-pressure side of the refrigerant circuit stops at the expansion valve.

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Function sequence, low-pressure side
Downstream of the expansion valve the depressurized refrigerant flows into the evaporator, where it evaporates due to its low pressure. It then changes state from liquid to gaseous.

The heat required for evaporation is taken from the ambient air. The cooled air is led to the vehicle interior via the blower motor (A32m1).

 To prevent the evaporator from icing up, if the temperature drops below a specific value at the evaporator, the refrigerant compressor is switched off by the control and operating unit. The evaporator temperature is recorded by the evaporator temperature sensor.