Automatic air conditioning refrigerant circuit, function - GF83.40-P-2005CE

MODEL 204.0 /2 as of model year 2009 /YoM 08

MODEL 204.3

MODEL 204.9

Fig 1: Identifying Automatic Air Conditioning Refrigerant Function Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Engine running
Air conditioning switched on

Automatic air conditioning refrigerant circuit, general

Control of the automatic air conditioning refrigerant circuit is performed by the automatic air conditioning control and operating unit (N22/7). The air in the vehicle interior is cooled according to the component settings. The individual components are interconnected through lines and form a closed system.

The automatic air conditioning refrigerant circuit consists of the following functional components:

Function sequence for high-pressure side
Function sequence for low-pressure side

Function sequence for high-pressure side

The refrigerant compressor driven by the engine draws in the cold gaseous refrigerant from the evaporator, compresses it, whereby it is heated, and delivers it to the condenser. The compressed hot refrigerant is cooled in the condenser by the outside air flowing past. On reaching the dew point dependent on the pressure, the refrigerant condenses and changes in terms of its physical state from gaseous to fluid.

The refrigerant flows from the condenser to the fluid reservoir (drier) via a line. While it flows through the fluid reservoir, the refrigerant is cleansed of any chemical and mechanical impurities in order to protect the subsequent components. The cleaned refrigerant then flows to the expansion valve. The liquid refrigerant, which is under high pressure, is injected into the evaporator.

Function sequence, low-pressure side

The liquid refrigerant decompresses in the evaporator and changes again in terms of its physical state from fluid to gaseous. The evaporation heat required for the evaporation is removed from the air flowing past at the evaporator fins, cooling it down in the process. The refrigerant, which is completely gaseous once more, is drawn in again and compressed by the refrigerant compressor. The cooled air is led to the vehicle interior via the blower motor (A32m1).

As of 1.12.09 a coaxial heat exchanger will be installed. This increases the output and efficiency of the refrigerant circuit.

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.

Overview of automatic climate control system components

GF83.40-P-9995CE