Truck stuck on Bi level blower vent

[82TexasBurban]

1982 Suburban. I finally got everything back up to speed A/C wise with the exception of the vent. It seems to be stuck on bi level ac. It blows great at floor but not so good out of the vents. It will switch between hot and cold, and it will go to "vent mode" but between max a/c and normal a/c and bi level it will not change. Any suggestions on this?

 

[British Slave]

Check the vacuum motor on the very left end of the heater/ac case. Use a hand vacuum pump, hook on to the vac motor and see if the door moves. You will have to remove the heater diverter duct . One screw and it's off. After removing the diverter, you can see the door that directs air from the floor to the dash vents. It may just be stuck. Poke it and see if it moves. lol.