The ACC unit controls a bank of switching valves that direct vacuum (so to speak) to the various vent actuators. The pink think you see in the dash is one of them. I'm not sure if you can get to the bank of switching valves through the center of the dash. IIRC you have to pull the right side panel of the center console. Check that there is sufficient source vacuum. Then check that each line holds vacuum. When you apply vacuum to a line, you should hear an actuator move a flap. You'll need a system diagram because some lines interconnect. Try mb.braingears.com if you don't have a factory manual.

This could go a lot of different directions but basically potential problem areas are:

- no source vacuum, major leak in the switching valve bank

- no signal from the PBU, unusual if there's proper blower control

- ruptured acutator diaphragms, unusual that all are bad

Could be other things.

Sixto
... stay tuned