If your BMW's air conditioner isn't blowing cold air, the first thing you should check is the compressor. The compressor is responsible for circulating refrigerant throughout the AC system. If the compressor is not working properly, it will not be able to effectively cool the air. There are a few signs that can indicate a problem with the compressor:
-The AC system is not blowing cold air
-There is a strange noise coming from the compressor
-The compressor clutch does not engage when the AC is turned on
-The AC system blows warm air when first turned on, but then blows cooler air after a few minutes
If you notice any of these issues, it's important to have your BMW's AC system checked by a qualified technician as soon as possible.