Vent defrost, actuator

[Phil750]

I am trying to fix the vent, defrost A/C.
1st where does these controls get vacuum from?
2nd What is the actuator? What does it do? How do you know if it's working?
My A/C is working fine except half comes out the floor heater half out the ducts. I took apart the cover to see the door. It was half open. I checked to see if there was vacuum at the actuator or the hose. Neither.
I temporarily closed the door with a small wedge. A/C comes out of vents only.
My manual does not cover this area in detail.
I'll take any and all ideas at this point.
Thanks Phil
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