Have a 04 F250 5.4l that the a. blows cold then hot. Over the winter I removed the condenser while doing some work. I put it back together with a new drier and orifice the system and put in 42oz of 134A. It was nice and cold then drove it the next day and it started off cold then went hot. Came home looked for leak as I have dye in it. It looked like the high side valve might have a slow leak. Replaced it clean any dye up evacuated it again and recharged it. Still the same issue. No leaks found and my pressures are good. When the truck turns off and the go an use it again it start off cold again. It does sometime get warm and the back to cld. What might the issue be??? Any help would be greatly apricated.

 

On your heater hose check for the climate/heater control valve, it should have a vacuum line on the front that opens and closes a valve in the heater hose. Check and make sure you have vacuum there and that it's opening and closing the valve.