midnightleadfoot

Hello.
Picked up my new to me olds today and it was cold and raining.
The heater works when I move the lever from heat to vent I get heat out of the floor then the dash vents but when I move to defrost.. I get nada out of the defrost vents but heat still comes out of the floor and dash front facing vents,, but mostly the floor..


What would cause this? What to look at/for?
The lever moves smooth , unlike my 71 truck that you can tell you are forcing the cable..


I'm guessing there is a flapper door that moves /directs the air.. that isn't.
Is this door moved by a cable or is it by a vacuum diaphragm/pod?


Thanks for any insight on this...