I have had a number of air con problems over the years. Most have had to do with the belt and the pulley on the end of the compressor. They were easy to fix.
The worst one was a failure inside the heater matrix which involved the whole of the dash being pulled out and the very large heater housing being replaced (luckily under warranty).
First thing to check is that the pulley and belt are still intact.
Note. It is advisable to run your engine once a month if the vehicle is not being used, with the air con on for at least 10 minutes to help obviate problems.
Cheers
