Refrigerant Circuit, Function - GF83.40-P-2008FG

Model 213 

up to model year 2021 

except code 1U6 (R744 refrigerant) 

Courtesy of MERCEDES-BENZ USA

Model 213 (except for hybrid vehicles) 

Courtesy of MERCEDES-BENZ USA

Hybrid vehicles 

Function requirements, general 

• Engine running (except for hybrid vehicles)
• Electric refrigerant compressor switched on (for hybrid vehicles)
• Climate control switched on

Refrigerant circuit in general 

The refrigerant circuit is regulated by the A/C control unit (N22/1).

The refrigeration circuit basically consists of the following components:

• Refrigerant compressor
• Condenser
• Accumulator (drier)
• Expansion valve (except for hybrid vehicles)
• Front evaporator shutoff valve (for hybrid vehicles)
• High-voltage battery cooling expansion valve (for hybrid vehicles)
• Evaporator
• Inner heat exchanger
• Heat exchanger (for hybrid vehicles)

The individual components of the refrigerant circuit are interconnected through hoses and pipelines and form a closed system.

The refrigerant circuit consists of the following functional components:

• High-pressure side 
• Low-pressure side 

The separation points for this are the valve plates on the refrigerant compressor and the injection valve on the expansion valve.

High-pressure side 

The refrigerant compressor 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 blow-by air or the outside air sucked in by the fan motor (M4/7).

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 then flows into the accumulator (drier). While it is flowing through the fluid reservoir, moisture is removed from the refrigerant, vapor locks are separated and any mechanical impurities are filtered out in order to protect the downstream components from these. The cleaned refrigerant flows onwards to the expansion valve (except for hybrid vehicles), to the front evaporator shutoff valve (for hybrid vehicles) or to the high-voltage battery cooling expansion valve (for hybrid vehicles). There, the liquid refrigerant which is under high pressure is injected into the respective evaporator.

Model 213.016/050/053/054/216 up to model year 2021

except code 1U6 (R744 refrigerant)

Through actuation of the expansion valve for the high-voltage battery cooling system, the refrigerant circuit is extended to include the cooling circuit for the high-voltage battery. If the high-voltage battery is cooled, the cleaned refrigerant flows through the heat exchanger and cools the high-voltage battery cooling system's coolant flowing through the heat exchanger.

Low-pressure side 

The liquid refrigerant decompresses in the respective 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 blow-by air 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 introduced by the electronic blower motor (A32m1) into the vehicle interior.

Model 213.016/050/053/054/216 up to model year 2021

except code 1U6 (R744 refrigerant)

If the high-voltage battery is cooled, the refrigerant changes its aggregation state from liquid to gaseous when flowing through the expansion valve. The gaseous refrigerant is then sucked in by the A/C compressor and compressed again.

To prevent the evaporator from icing up, the refrigerant compressor is switched off by the climate control control unit when the evaporator temperature undershoots a certain point for model 213 (except for hybrid vehicles). In hybrid vehicles, the climate control control unit actuates the evaporator shutoff valve accordingly. This enables the refrigerant compressor to continue to be operated. This is necessary to ensure that the high-voltage battery can also be operated at outside temperatures below 10°C.