When I start my car and I turn on the AC it works fine but after about 4 minutes then the AC clutch stops and starts more frequently until finally it does not work. If I turn the car off and re-start it, the AC won't work. If I let the car cool down for an hour or two and then start it, turn the AC on then it will work for about 4 minutes and then eventually the compressor clutch will not engage (increasing the start and stopping of the compressor clutch until it won't engage). I tried replacing the relay switch but that was not the problem. Any ideas? Thanks.