Refrigerant circuit function

S83.40-4571-79

S83.40-4573-79

Function requirements, general

 "Engine running"

 Climate control switched on

 Model 447.6/7
with code HH4 (THERMOTRONIC automatic climate control)
Model 447.6/7
with code HH9 (Air conditioner, automatic heater control)
Model 448.7
with code HH4 (THERMOTRONIC automatic climate control)
The CDI control unit (N3/33) or ME-SFI [ME] control unit (N3/34) sends the "Engine running" signal via chassis CAN (CAN E), electronic ignition lock (EZS) control unit (N73) and interior CAN (CAN B) to the air conditioning control and operating unit (KLA-V&KLA-H) (S98).

 Model 447.8
with code HH4 (THERMOTRONIC automatic climate control)
Model 447.8
with code HH9 (Air conditioner, automatic heater control)
Model 448.8
with code HH4 (THERMOTRONIC automatic climate control)
The CDI control unit (N3/33) or ME-SFI [ME] control unit (N3/34) sends the "Engine running" signal via chassis CAN (CAN E), electronic ignition lock (EZS) control unit (N73) and interior CAN (CAN B) to the automatic air conditioning (AAC [KLA]) control and operating unit (N154).

Refrigerant circuit in general

Regulation of the refrigerant circuit is carried out by the automatic air conditioning (AAC [KLA]) control unit on model 447.8 or model 448.8 and by the air conditioning control and operating unit (KLA-V&KLA-H) on model 447.6/7 or model 448.7.

The refrigerant circuit with CODE HH9 (Semi-automatically controlled A/C, TEMPMATIC) or with CODE HH4 (THERMOTRONIC automatic climate control) essentially consist of the following components:

 Refrigerant compressor with magnetic clutch

 Condenser

 Accumulator (drier)

 Expansion valve

 Evaporator

 Inner heat exchanger (with CODE HH4 (THERMOTRONIC automatic climate control)) in MODEL 447.7/8

With CODE HZ7 (Semi-automatically controlled air conditioning, TEMPMATIC in rear) the following components are also available:

 Evaporator shutoff valve

 Rear air conditioning 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 on the refrigerant compressor with magnetic clutch, the injection valve on the expansion valve and the injection valve on the evaporator shutoff valve.

High-pressure side

The refrigerant compressor with magnetic clutch draws in the cold, gaseous refrigerant, 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.

The refrigerant changes its state from gaseous to liquid. The refrigerant then flows into the accumulator. The refrigerant is dehumidified when it flows through the fluid reservoir, vapor locks are separated and mechanical impurities are filtered out in order to protect the downstream components. The cleaned refrigerant flows on to the expansion valve (with CODE HH9 (Semi-automatically controlled A/C, TEMPMATIC) or with CODE HH4 (THERMOTRONIC automatic climate control)) where the liquid refrigerant which is under high pressure is injected into the evaporator.

With CODE HZ7 (Semi-automatically controlled air conditioning, TEMPMATIC in rear), the cleaned liquid refrigerant which is under high pressure also flows to the evaporator shutoff valve and is injected into the rear air conditioning evaporator (evaporator shutoff valve actuated or opened).

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 now completely gaseous again is drawn in by the refrigerant compressor with magnetic clutch and compressed. The cooled air is led to the vehicle interior via the blower motor (M2).