I have zoned control ac/heat unit controlled by 2 thermostats (1 upstairs/1downstairs) to a central board (aprilaire 6202). So this is supposed to allow me to control upstairs and downstairs serately as 2 zones with the same unit. What I observed is that at any time the unit turns on regardless of what t-stat triggers it to turn on... volume of air released down/up stairs is consistent however upstairs seem to get less through the vents. Now I went to attic to check out the dampers and see if I can visually see these things in action to better understand. However, what I noticed is not what I expected.

First I noticed that both dampers have a lever with the word "close" on one side. Damper 1 (the one associated with upstairs) I was able to manually slide lever back and forth from the close position. Damper 2 (associated with downstairs) I was not able to manually move from the "close" position. I manually triggered downstair t-stat and ran to check if any movement on either damper and nothing... both were still in closed position. Then tried the same with upstairs t-stat to trigger... and checked the dampers and did not notice movement. My expectations were because the wiring from each damper was going to the "NC" on control board that it meant that the damper was "normally closed" and that if triggered the each motor would open the damper depending on which t-stat was calling for air.. And all this should could visually checked out. I took some pictures to kind of show the pieces to the unit I have and hopefully someone can explain how this should work and how can I got about to test this. Now you will notice one of the dampers I manually moved the lever from the close position when I took the picture but it was always in the close position prior to picture.

The dampers seem to have a motor made by syncron with 645 24V 60HZ written on side... not sure who made the damper itself as I can't seem to see it as it is within the flex tube thing.