My AC has not blown consistently cold at highway speeds for about 2 years now but today on my way back from Junction, TX going back home to Kingsville, the AC started getting worse. The AC only blows cold when the truck is accelerating or going up a hill but when slowing down or going downhill, it will start to blow hot, almost like the heater is on. With the cruise control set, the AC will go back and forth between hot and cold on level ground. It probably didn't help the AC any that it got up to 100 degrees ambient temperature today on my way home. So my question is what does everybody think could be wrong with my AC? Just needs freon? Maybe a problem with the compressor or condensor? Any help will be greatly appreciated and thank you in advance.