Audi Repair: 01 Audi a4 quattro 1.8t- a/c problems and engine, audi a4 quattro, audi a4

Question
I just purchased a used 2001 Audi a4, after driving the car for about 5-10 minutes the A/C blows hot air. Also, after driving about 45 miles, i turned off the car. Then tried to restart it, and it wouldn't start all i heard was the "click" sound. I tried later once the engine cooled, and it started right up and the A/C worked, but then stopped working after a few minutes. What could be the problem? since I have NO idea about cars especially Audi's

Answer
Most probably the refrigerant is low, causing the compressor to switch off.  If the car does not start, this could be an overheating issue, or the starter is malfunctioning.  Since it started when the engine cooled down, is this a recurring problem?  Let me know,  Jan