1995 Dodge Caravan a/c not working correctly

I have a 1995 dodge caravan v6. when the a/c is turned on it squealed and locked up the compressor. I though it needed a new one. i replaced it..not once but twice. at the end all 3 compressors did the same thing. once installed as you add 134-a clutch kicks in and compressor starts. then once you add less than a can it locks up. there are no leaks. did this with all 3 compressors. if you let some of the freon out the system appears to run and engage fine...just not cold.you can hear the clutch and compressor kick in...but it builds up pressure and locks the compressor. I want to know if this could be some type of valve or expansion valve. something like a switch or release. if you can tell me anything please tell me