2000 Dodge Caravan heater and air conditioning

Air Conditioning problem
2000 Dodge Caravan 6 cyl Front Wheel Drive Automatic

Bob and Ken,
I have another question with regards to my vehicle's heater. When I turn the heater and blower "on", I hear a clicking sound inside the dashboard or behind the heater and air condition switches and it seems that it is blowing a freon. And when the heater is on and on the defroster mode, the air condition compressor or clutch is engaging. One more thing, when the AC is on, I can see like a mist coming out from the vents. What must be the problem?
Thank you very much.