Auto Air Conditioning & Heater Repair: 97 Blazer-ac only blows out of defrost vent, dash area, original system

Question
I have a S10 1997 Blazer.  It has 150000 miles on it the other day a/c was fine.  Today when I turned on the a/c to high the air was only coming out the defrost vent.  It was still cold, the other vents blew a little, but barely.
Also before all this the air never got as cold as with the original system (system was replaced a few years ago).  I know the freon levels were fine but I generally have used windows.
Thanks
mike  

Answer
Sound like two problems going down. First, you have a vaccum leak that is affecting your vent control system.Check a main vacccum line that feeds the system.It comes in from right side of dash area and into the vehicle.
Second,have the system check for low freon level-possible leak or leaks with that age and mileage.

good luck,davidt