How to troubleshoot the air conditioning system in an Audi A4?

My Audi A4's air conditioning is not working properly, it's blowing warm air instead of cold. What could be the possible reasons and how can I fix it?

First, check the refrigerant level in the AC system. If it's low, it could be due to a leak. In that case, you should have it repaired by a certified mechanic.

Another common reason for AC not working is a faulty compressor or condenser. Have a mechanic inspect and replace these components if necessary.