I have a '96 GRand Cherokee Ltd with an Automatic Temperature Control (ATC) where the desired temp is displayed and the system does its magic to keep it there. I took it to the dealer for diagnosis. They said it was 12 ounces low on R134a and had a leak in the evaporator. The last time the evap leaked, about two years ago, it was replaced. I hate to think that the new one is really leaking. The symptoms it showed THEN were increasingly warm air until the compressor would no longer engage. Since the dealer thought it was low on R134a, I gave it exactly 12 ounces. I don't know where they came up with that figure, but figured it would blow cold if low refirgerant were the cause. That didn't fix it. I have also tried another ATC module (actually three from two different salvage yards) None of them would even make the AC fan blow. They could have been faulty, as they were removed from Jeeps that had been out in the weather for a while, but I have no way to know. Most of the time, when it decides to blow HOT, turning the temp control knob all the way to hot and back to the desired temperature will cause it to blow cold again. Other times turning the ignition OFF and the AC off before restarting the engine will make it blow cold. THOSE work arounds worked before I put more R134a into it too.
Has anyone here experienced this same sort of problem? If so, what was the fix?