I have a '98 TJ w/ A/C. In fan position 1, 2, or 3 sometimes it will start blowing warm air. It has not done it in fan position 4 yet. Actually when it starts blowing warm air in either 1, 2, or 3, when I switch it to position 4 it will start blowing cold again in a minute or two. Any guidance as to what to look for. I already had it to a shop and they said it didn't need a charge. They thought maybe the belt was slipping. After tightening the belt and then replacing the belt it still does it. Any help appreciated.