How to troubleshoot a faulty air conditioning in an Audi 80?

I am having issues with the air conditioning system in my Audi 80. It blows only hot air and there is a strange noise coming from the AC when I turn it on. What could be causing this problem and how can I fix it? I am not very familiar with cars, so any help would be appreciated.

The most common cause of this issue is a low refrigerant level. You will need to have the AC system recharged by a professional mechanic. It is not recommended to try and do it yourself, as it involves handling refrigerant which can be dangerous.