I have used the Search button for this topic so please don't flame me. My car just recently started doing this. I start the car and then turn the a/c on, the pump kicks on then kicks back off 5 seconds later and then comes back on. It goes on and off at 5 second intervals. The vents blow scorching hot. I checked the pressure of the system it goes from green to blue. Green meaning refill, blue meaning charged. It green when the pump is off and blue when the pump is on. This thing drags horribly on my engine too. makes the car sound like its cammed out crazy like a drag car. Could the problem possibly be the a/c compressor clutch circuit. It does this when I try to run defrost also.