A/C problems '02 JGC

I have a 2002 Grand Cherokee LTD 4.7. I recently had the blend/recirc doors repaired or replaced. The previous owner had destroyed the doors by screwing 3" screws through them to secure them in the up position to get heat ALL THE TIME. Now that the door are repaired, I want to use the A/C. It will blow ice cold at start up and continue to blow cold even with the engine reaching normal running temp until I shut the engine off. If I restart the engine within a short period of time, before the engine cools off, the air blows HOT. Once the engine cools off, the air will blow cold again. HELP!! What could be the problem here?