How do I troubleshoot my Audi A4's faulty air conditioning?

My Audi A4's air conditioning has suddenly stopped working. I've checked the fuses and they seem to be fine. What else should I look for? Any suggestions on how to troubleshoot this issue?

First, check the refrigerant levels in your air conditioning system. Low levels can cause the system to malfunction.

Another common issue with Audi A4 air conditioning is a faulty compressor. Make sure to have it checked and potentially replaced if necessary.

If the air conditioning is blowing warm air, it could be a sign of a clogged or dirty air filter. Try cleaning or replacing it to see if it helps.