No cold air AC Compressor clutch is engaged Low pressure is "0" tried to add Freon and immediately jumps to 150 psi relieve pressure and again immediately back to 0 with clutch still engaged never seen this before - how can the clutch be engaged with no pressure on LP side?
Most likely the system is plugged. You never state what your high side reading is ... more than likely it would scare you if you did see it. If it's plugged and you still have pressure on the high side, I can see that it might engage that way. It definitely wouldn't be good to run it too long that way. You also wouldn't see anything in the way of cooling going on, either. You don't mention anything about the vehicle in question, so can speculate no further on where that plug might be or what's going on beyond that.