A/c compressor?

My 1996 mercury villager has front and rear a/c. The front was blowing warm air and the rear was cold. I played with the fuses, relays, and all plugs under the hood, along with the door under the dash. Now all is cold, but is sound like the compressor is kicking on and off too quickly. We put a small gauge from a can of freon and it shows that the freon is full. Why is the compressor clicking so frequent? I have already replaced the belt.