Buick/Olds: 1989 Buick Century - Moist Cool AC After Conversion, freon 12, buick century

Question
Just had the system changed over to 134a from Freon-12 because I had to get compressor changed.  Changed orifice tube, accumulator/drier and had system purged and cleaned by shop.  Air from vents is cool, but seems moist/damp.  AC is a closed system, so suspect that there must be a buildup of water in evaporator case?  Is there a drain plug/hole I could check?  How can I find it?  Is it possible that where metal tube goes from accumulator into evaporator that some water is getting past caulk? that is built up around area?  Any other thoughts?  Shop says air is cold, I agree, but I also know it is not dry.  Thanks.

Answer
Any time you get moisture in the a/c system the expansion valve freezes.However you could have moisture in the unit under the dash, where the air blows across the exchange unit. (rain water) It could be in the vents. just check for leaks from around the windshield, etc.