Heres the deal. My a/c will run great for about 15 minutes or so (in stop and go traffic on the highway its fine) but after those 15 minutes are up it starts to go warm. Now if you turn it off and then turn it back on (once i'm moving) it starts blowing cold air again. I've had my freon filled, I replaced the evaporator.A few days ago I took it to nissan for a diagnostics check. They said it was the thermistor(?) That sits inside the evaportor. So I bought the part and had my mechanic put it in. Once again it worked great for the first 15 minutes then it went warm again! What can I do? Is there any other thermistors? PLEASE HELP!