Air flow doesn't change in car when turning dial?

It's hard to explain, but when I switch around the air flow with my cars dial thing, direction doesn't change. For example, when I set it to feet vents only, it ll come out of front head vent and defroster. If I switch to primarily defroster, it will still come out of both vents. It's like the dial does absolutely nothing to change the airflow. I have a 2000 Honda Civic Ex sedan.

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