A couple weeks ago I noticed the a/c wasn't blowing cold air. I went to recharge it and noticed the pressure was high. I took it in to a shop and they found a small leak some valve. They replaced it and refilled the freon. Everything worked for a day or so. Then my wife noticed that it could blow cold air, and then quit all at once almost like the vent was on. I took it back to the shop and they checked it out and said everything checked out and the a/c was blowing 32 degree air. Today on the way home from church (about 10 miles), we got in the car, turned the air on. It slowly began cooling the further we went. Then almost instant the temp dropped (probably to the 32 degrees). After a couple miles though it almost instantly went back to warm like we had the vent on. Any ideas as to what it might be? The car isn't overheating or anything. The shop (Firestone) said they checked everything (compressor and such). Could it be some temp sensor or something? Please let me konw what you think it could be and how easy it would be for me to replace. Thanks!!!