How to fix a malfunctioning air conditioning in the Audi A2?

My Audi A2's air conditioning has suddenly stopped working. The air is not cold and there is a strange noise coming from the AC unit. Can anyone suggest any troubleshooting steps to fix this issue?

First, check the AC fuse in the fuse box to see if it's blown. If so, replace it with a new one. If the fuse is fine, then it could be a problem with the compressor. Try turning on the AC and see if the compressor is engaging. If not, it may need to be replaced.

Also, check the refrigerant levels. Low refrigerant can cause AC to malfunction. If the levels are low, take your car to a professional mechanic to have it recharged.

Another possible cause could be a faulty AC control switch. This switch controls the AC system's functions and if it's damaged, the AC won't work properly. You can test this by switching the AC on and off a few times to see if the air flow changes. If not, then you may need to replace the AC switch.