95 E320 A/C keeps turning off
 

When the A/C turns on - it gets very cold. But it runs for awhile then the compressor turns off and it starts blowing hot air. It may run for an hour; it may run for five minutes, but it never stays on. If I wait, sometimes it will turn back on all by itself. Usually I have to turn off the system, and then try restarting it. If I try this about ten times, I get A/C again. The outside temp or the temp setting on the controller seem to have no bearing. The fan blowers are fine.

Repair-wise, I've had the Freon level checked and have replaced the controller.