How to fix the air conditioning in an Audi A2?

My Audi A2's air conditioning is not working properly. It blows out warm air instead of cold. What could be the cause and how can I fix it?

The most common reason for an air conditioning unit blowing warm air is low refrigerant levels. Check the refrigerant level and if it is low, you can try topping it off yourself with a recharge kit. If that doesn't work, it may be time to take it to a professional mechanic.