What are the reasons for poor air conditioning cooling effect in BMW?

[OEden]

Insufficient refrigerant in the air conditioning system / The refrigerant pressure switch detects low pressure or the pressure switch is faulty; Air conditioning compressor failure; Air conditioning control unit failure; Air conditioning function switch failure; Air conditioning system wiring harness open/short circuit failure. Here is additional information: 1. Air conditioning working principle: The air conditioning system mainly works by compressing gaseous refrigerant into high-temperature and high-pressure gas through the compressor. The gas then flows through the pipeline into the condenser, where it is cooled by the radiator fan and condenses into high-pressure liquid refrigerant. The high-pressure liquid refrigerant enters the dryer reservoir through the pipeline, is dried and filtered, and then flows into the expansion valve for throttling. Its state changes drastically, turning into low-temperature and low-pressure liquid refrigerant that enters the evaporator. Inside the evaporator, it absorbs heat from the air flowing through it, lowering the air temperature and blowing out cold air, thereby producing a cooling effect. 2. Refrigerant working principle: The refrigerant itself evaporates into low-temperature and low-pressure gaseous refrigerant after absorbing heat, and is then sucked into the compressor through the pipeline for compression. As long as the compressor continues to work, the refrigerant circulates continuously in the air conditioning system, producing a cooling effect. When the compressor stops working, the refrigerant in the air conditioning system stops flowing, and no cooling effect is produced.