Air Condition Problems on 1997 Pontiac Grand Prix GTP

When I turned on my a/c the air is not blowing out of all the vents. Out of the five vents on two are blowing cold air. Now, is there some type of flapper door that is suppose to open and close depending on what you have the switch set on whether it a/c or heat? Also, when I have it on a/c and high cold air is blowing out of the defroster.

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2 answers
Im troubleshooting the same problem at the time and I can promise u it's not the flapper doors
check for vacuum leaks