It is so hard to find the appropriate names for the different doors. The flap that has two elements is not the door I'm talking about. The recirculate actuator has two vacuum lines to it and is in the center. It closes the door above the blower. The first one I found by blocking the door under the hood. (I don't actually do the work so I'm a little rusty on actual locations). I am involved with the diagnostic plan all the time and I remember we tested the first one by blocking the door from the outside.
Bosch Master, ASE Master, L1
33 years MB technician