hmmm, what do you mean by variable air damper? Cause just this past weekend my friend was playing with my hot/cold ac on/off and eventually the system got confused to the point where it stayed on hot air all the time. If I turned the knob to cold, even after turning the fan off and on, it wouldn't move. I ended up turning the car off, waiting for 20 seconds, and turning it back on and now it switches from hot to cold as normal.
Perhaps we're talking about the same mechanism? Except yours maybe went bad while my computer just got confused as to its position?
<rant>Never let your friends touch your car, that's 4 times now (at least) that my friends have or have nearly broken something on my car... ;)</rant>