Refrigerant circuit function

P83.40-5095-78

P83.40-5096-78

P83.40-5125-79

Function requirements, general

 Engine running (except model 166.063)

 Electric refrigerant compressor running (model 166.063)

 Climate control switched on

 MODEL 166.063
as of model year 2016
Detailed information on cooling of the high-voltage battery (A100g1) is available in the separate function description for the hybrid drive system in the high voltage on-board electrical system cooling function.

Refrigerant circuit in general

Control of the refrigerant circuit is performed by the automatic air conditioning control and operating unit.

 Detailed information on the climate control regulation function is available in the "Climate control regulation, function" subfunction.

The refrigeration circuit basically consists of the following components:

 Refrigerant compressor (except model 166.063)

 Electric refrigerant compressor (model 166.063)

 Condenser

 Accumulator (drier)

 Expansion valve (except model 166.063)

 Front evaporator shutoff valve (model 166.063 or CODE 582 (Rear air conditioning system))

 Rear air conditioning evaporator shutoff valve (with CODE 582 (Rear air conditioning))

 High-voltage battery cooling expansion valve (model 166.063)

 Evaporator

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 at the respective refrigerant compressor and the injection valve at the expansion valve.

High-pressure side

The respective refrigerant compressor draws in the cold, gaseous refrigerant from the evaporator and 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 then flows on to the expansion valve (except model 166.063), to the front evaporator shutoff valve (model 166.063, model 166.8 with CODE 582 (Rear air conditioning system)) or to the rear air conditioning system evaporator shutoff valve (with CODE 582 (Rear air conditioning system)) or to the high-voltage battery cooling expansion valve (model 166.063). The liquid refrigerant which is under high pressure is injected into the respective evaporator there.

 MODEL 166.063
as of model year 2016
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. This means that the high-voltage battery can be cooled by refrigerant. 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 respective refrigerant compressor. The cooled air is led to the vehicle interior via the blower motor (A32m1).

On vehicles with CODE 581 (Automatic air conditioning), cooled air is also introduced in the rear area through the rear blower motor (M2/1).

On vehicles with CODE 582 (Rear air conditioning system), the rear air conditioning blower motor (M2/29) also routes air through the rear air conditioning system evaporator.

 MODEL 166.063
as of model year 2016
If the high-voltage battery is cooled, the refrigerant changes its aggregation state from liquid to gaseous when flowing through the high-voltage battery cooling expansion valve. The gaseous refrigerant is then sucked in by the A/C compressor and compressed again.

 To prevent the evaporator from icing up, when a specific evaporator temperature is undershot on model 166, 292 (except model 166.063), the refrigerant compressor is switched off by the automatic air conditioning control and operating unit (N22/7). On model 166.063, the automatic air conditioning control and operating unit actuates the front evaporator shutoff valve accordingly. This enables the electrical A/C compressor to continue to be operated. This is necessary, to ensure that the high-voltage battery can also be operated even at outside temperatures of T < 10 °C.