my 1990 civic only blows air from the defrost and floor. when i select vents i get no airflow. Are our cars vacuum controlled (usually this happens on 1990's cars when they lose vacuum to the control unit)???

Any ideas? My search was unfruitful.

 

I know the fan speed has a resister that goes out and you only get certain speeds. Is the blower selection similar? Or is it strictly mechanical.

 

On hatches, the vent selection is cable controlled. The cables have a notch at the end that sits in a clip that keeps them from sliding as you change venting selection. Since the "Vent" position is the leftmost position, I can think of 2 possibilities.
1. The clip that holds the cable broke. So when you're trying to select "vent", the cable just slides out of position, not allowing the "vents" to open.
2. There is something blocking the airflow in the "Vent" position.

When you have it in the 'Vent' position. do you still get airflow from the floor?
If so, the most likely is the clip broke and the cable is sliding in it's holder.

 

I agree its most likely this ! when its broken, you might feel you vent "selector" free/loose
can you ear the trap moving when you are moving the selector ?