Fig. 10.5. Compressor (in section) with oscillating disks and six pistons: 1 – main control valve; 2 – electromagnetic clutch; 3 – belt pulley; 4 – rocking disc; 5 – piston; 6 – compression chamber
The car is equipped with a compressor with oscillating washers. It is located on the left side of the engine and serves to compress the refrigerant under pressure (about 1 kg), which is in a gaseous state. The compressor is driven by a belt drive from the crankshaft. When compressed in the compressor, the refrigerant changes to a liquid state and is fed to the evaporator, located in the heater housing under the instrument panel. There, the refrigerant evaporates again with the absorption of energy, due to which cold is formed. The air flowing past the evaporator is cooled by its plates. Then the refrigerant is fed back to the compressor (Fig. 10.5). For its better condensation after compression, two additional fans are installed in front of the condenser. The cooling capacity of the air conditioner is regulated electronically and depends on the outside air temperature, the interior temperature and the set value of the desired temperature.
Additional information about the air conditioner
Fig. 10.6. Access to both additional fans is opened after removing the radiator grille
The additional fans (Fig. 10.6) have two speeds. At a coolant pressure of 20 bar, the switch is triggered. Then the relay is triggered, and the additional fans receive voltage via the preliminary resistors. At a coolant temperature of more than +107°C, the fans operate at maximum speed.
When the compressor is turned on, the idle speed setting of the engine is immediately changed so that it does not stop. The compressor consumes about 9 kW.
To avoid thermal overload of the engine, when the coolant temperature is about +115°C, the compressor is switched off.
(Material based on data from the portal: www.mercedesman.ru)
The air conditioner control unit receives information about the compressor speed from an inductive sensor. The engine speed data comes as a TD signal from the Motronic system. If the obtained ratio between the two values is outside the specified range, this may mean that the compressor is rotating with difficulty and the auxiliary drive belt is slipping on the pulleys. In this case, the compressor is switched off protectively.
When removing the engine, the closed circulation system of the air conditioner working fluid, which is under high pressure, should not be opened without special equipment. Topping up the refrigerant in the system is only possible at a service station. Therefore, when removing the engine, it is recommended to unscrew the compressor and system pipes from it together with the brackets and secure them to the side in the engine compartment with wire.
The air conditioner control unit has a self-diagnostic system. Information about any malfunctions that have occurred can then be read from the device's memory at the service station.