My air conditioner on my truck works really well most of the time. The air if very cold. However, out of the blue from time to time, it will turn off and the air will come out somewhat hotter than outside. I can't link this to any behavior or specific circumstance. For example, it is not connected to whether I am accelerating or not, and it doesn't seem to be related to the normal on/off cycling that they do. After a little while it will start blowing cool again. Is this perhaps a "Freon" level issue. Any suggestions will be helpful thanks.