1997 Buick Riviera Supercharged A/C Problem

1997 Buick Riviera Supercharged, Automatic, 2WD, 123,000 miles.

I have a problem with the A/C. When you first start the car, the A/C compressor starts working and runs fine for about 4 minutes, then it stops working and the car begins to blow hot air. I had the A/C system checked and was told by the A/C experts that they would have to go into troubleshooting the electrical system because there were no leaks at all in the actual A/C componets, that it could be one of the many sensors turning it off.

I then took it to the dealer so they could check it out and they told me that the problem was the compressor itself, that it was going bad and that it needed to be replaced. I bought a compressor and just had it installed and the system serviced. They A/C worked for abou 5 minutes and went back to doing the same thing.

What in the world is going on? Does this thing have a lot of sensors that go bad or what? I can't figure that out and need help. Maybe someone had the same experience and want to share a solution with me. It costs me money every time someone checks it out.