my 01 supercrew having a problem with A/C going back and forth from cold to hot, and some days wont come off hot, yet the other day drove 2hours and got good cold air the whole time, pressure on low side is about 25 put entire 16 oz can of 134a in. any suggestions would help. also the heater would not adjust at all, strays hot. I also replaced the temp cont. switch.

 

If you are having both heat and A/C problems then you need to look at the blend door. It sounds like a vacuum problem.