Why does my A/C just blow out the top vents

[ToocoolZ28]

My 89 Camaro just blows the cool A/C air out the top defroster vents. Is there a way to fix this or at least jerry rig it so it will blow out the lower vents?
Thanks.
Ron

[Parker_'915spd]

check your vacuum lines....the all the heater switches are run off a vacuum system