1 - fan
2 - evaporator
3 - throttle
4 - place of connection to the low pressure circuit during maintenance
5 - point of connection to the high pressure circuit during maintenance
6 - dryer tank
7 - capacitor
8 - compressor
a - counter air flow for cooling the condenser
b - removal of heated air to the environment
c - uncooled air flow through the heater fan
d - the flow of cooled air into the car interior
A - high pressure circuit (gaseous refrigerant)
B - high pressure circuit (liquid refrigerant)
C - low pressure circuit (liquid refrigerant)
D - low pressure circuit (gaseous refrigerant)
The air conditioning system can lower the interior temperature below the ambient temperature. The fully automated system maintains any set temperature unchanged, the distribution of air flows and the amount of incoming air are regulated by the electronic control unit, regardless of the speed of the vehicle: information about the air temperatures in the cabin and outside is transmitted to the control unit using various temperature sensors. Along with this, in accordance with the program-set values, the actuators control the position of the air dampers and the performance of the fan, thereby regulating the climate in the cabin. In the event of malfunctions in the operation of the control unit, sensors and executive links, the corresponding fault codes are entered into the accumulator of fault codes of the control unit. When troubleshooting in a workshop for BMW vehicles, these codes can be read using a special diagnostic tool.
Operation of the air conditioning system
The compressor is driven by a V-ribbed belt from the crankshaft. It increases the pressure in the circulation circuit to 30 bar, whereby the gaseous refrigerant is heated. Washing condenser air (cooling air stays outside) removes heat, as a result of which the hot gas cools and condenses - the refrigerant becomes liquid. It flows under the still high throttle pressure, after which the pressure decreases. In this case, the refrigerant in the circulation circuit expands and at the same time cools even more. In the evaporator, the refrigerant removes heat from the air surrounding the evaporator, causing the air to cool. This cooled air then enters the interior of the car. Due to the heat received in the evaporator, the refrigerant becomes gaseous and enters the compressor under low pressure. Thus, the refrigerant circulation process continues.
Attention: Repair of the air conditioning system is not described. All work on the air conditioning system must be carried out by a specialist workshop. Under no circumstances should the refrigerant circuit be opened, as frostbite may occur if it comes into contact with the skin.