My AC wasn't working right for a couple of years. I took in in for the condenser recall but it still wasn't working correctly. It would get cold at first but after a few minutes it would blow warm air. I had to figure it out myself. The AC clutch was the cultprit. It would engage initially but would stop working after getting hot. When your AC is not working, pop the hood while it's still running and see if the compressor is spinning. If not, there's your answer.