1997 s10 vent doesnt work A/c floor defrost...Info PLEASE

I have a 1997 s10. The a/c will blow out the floor and out the defrost. however, in no selection mode will it blow anything hot or cold out the vent. I was able to remove one of the covers on the floor part of the unit and the white flapper door moves freely by hand. I have moved it up and down and can control the amount of air that passes through defroster or floor vents, but in no position doany of the pasasenger vents ever blow any air. What controls the airflow to the vents? Is it vacuum or is it part of the electrical switch? How can you check it??

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Thank you.
Steve

IM having the same problem with my 1993 blazer, air blows out of the floor and defrost but nothing out of the vents, can you please email me what you found??, or just post here

Thanks [email protected]

find the vacuum reserve....it looks like a ball...pull off the hose and blow cigarette smoke in it...it will show you where the leak is
b

sounds like bad vaccuum hose or such going to vaccum ball. ball could be shot too. bypass the ball and check valve, truck idling, see if controls work. to bypass, should be able to slip hose going into truck over hose coming from motor with a little lube(spit). if now works, bad ball or check valve, easy fix. jon

The switch is the problem on 4x4s.The vacuum hose that goes to the switch is connected to the transfer case and is known to get oil from the case which then messes up the switch.