How to fix a malfunctioning air conditioning in an Audi 80?

The air conditioning in my Audi 80 has suddenly stopped working. No matter how high I set the temperature, it only blows out hot air. What could be causing this issue and how can I fix it?

It is possible that the refrigerant in your air conditioning system has leaked out, preventing it from producing cold air. Have it checked and refilled by a certified mechanic. In the future, make sure to regularly check the level of your coolant to avoid this issue.