BMW X5 heater control problem

[Busser]

I have a 2001 X5 3.0i with standard heater controls. When I move the air blend knod to the floor position, nothing comes out of the floor vents. I can hear a lot of air coming from within the dash. Before I 1) start taking the dash apart, or 2) Head to the local dealer, is this system vacuum operated or electrical? The older 7 series cars had problems with the tabs that held the actuator arms on the air blend doors deep within the dash breaking and causing a similar issue. I hope this is not the case, as it was a very expensive repair.....