What are the reasons for the BMW 3 Series air conditioning not cooling?

[Branden]

BMW 3 Series air conditioning not cooling reasons and solutions are as follows: Insufficient or low refrigerant: It may be caused by a small refrigerant leak. You can observe it from the sight glass on the dryer tank. When the air conditioning is running normally, if there are continuous and slow bubbles in the sight glass, it indicates insufficient refrigerant. If obvious bubble flipping occurs, it indicates severe refrigerant shortage. In this case, simply add refrigerant. Loose drive belt of the car air conditioning compressor: If the drive belt is loose, the compressor will slip during operation, leading to reduced transmission efficiency and a decrease in compressor speed. This results in reduced delivery of compressed refrigerant, causing the car air conditioning to not cool. If the compressor drive belt is too loose, it should be tightened. If it cannot be turned by hand, it means the belt is too tight and should be loosened slightly. If tightening is ineffective, or if the drive belt has cracks, aging, or other damage, a new drive belt should be replaced.