Auto Air Conditioning & Heater Repair: 1972 Monte Carlo A/C not blowing cold air, blade area, pivot point

Question
I recently purchased a 1972 monte and had the a/c worked on....The shop charged it with R-12 and made sure the compressor was working..Everything in the engine appears to be working and you can tell there's cold air going into the heather core because the if you touch the metal line its cold....However, there's just normal air coming through the vents...The blower moter seems to be working..I'm at a loss as to why there's no cool air flowing inside the car.possible blockage??

Answer
there is a pivot link on top of the heater case behind the glove box just to the left kindda L shaped they break somtimes- the heater blend cable is attached to it but the pivot point may be broken  also the vent defrost doors are vacuum controled may be pulling outside air even in max possition check w engine running see if air is being drawn in on passenger side just below wiper blade area - a outside vent screen is in that area