What was found
PILOT FLYING BACK, NOTICED AIR CONDITIONING WAS BEGAN BLOWING HOT AIR, HE THEN SWITCHED FROM AC TO FAN & BACK TO AC. THEN HE NOTICED THAT THAT GREY SMOKE STARTED TO FILL THE CABIN OF THE ACFT. NO ELEC SMELL WAS NOTICED. PILOT PERFORMED AN UNSCHEDULED LANDING. ACFT WAS THEN INSPECTED & DETERMINED THAT THE VISIBLE GREY SMOKE NOTICED WAS THE SYS DISCHARGING THE R134 INTO THE AIR CONDITION VENT SYS. NO ACTUAL BURNING OF ANY KIND OCCURRED IT WAS A THE R134 VAPOR, THE AIR CONDITIONING DISCHARGE LINE BURST NEXT TO THE PYLON DECK, LT SIDE NEXT TO THE AIR CONDITIONING COMPRESSOR. THE LINE WAS REPLACED & SYS SERVICED WITH R134, FUNCTIONALLY TESTED & FURTHER DEFECTS NOTED.