Centex Townhome - Heat/Cool Channeling Issue

We are in a townhome that has 3 levels, and the heat/cooling ducts run in 2 levels (on the ceiling in the bedrooms upstairs, and under the floor on the living area).
Centex provided a lever in the unit in the basement that allows for the air flow to be channeled to either of the two or to a mix of the two (depending on the position of the mechanical lever).
I found that one end of the lever works well (all the air flow is channeled completely to the bedrooms), but the other end does not shut it off completely. In my neighbor's home the channeling works well.
To give an example, in Winter, the bedrooms get really hot (while I would love to shut off the hot air flow to the top floor completely, and let it in the living area, from which it will eventually reach upstairs due to the hot air).
Has anyone seen this issue before, and any thoughts?
SR.
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All it consists of is a lever connected to a piece of metal inside the duct. It shouldn't be too hard to figure out why the metal isn't moving from completely open to completely closed. But, I doubt you would want it completely closed. In general, it's ok to do some balancing, but you still must have a reasonable amount of air volume moving through the furnace, so I doubet you would want a major duct closed anywhere near completely.
It's possible the lever is not connected to anything.
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