Remove the three screws (1) (head type TORX), disunite a socket (3) and remove the electrical motor (M2 / 4) drive the air damper to the housing heater / evaporator (in the area of the bulkhead).
Installation is in the reverse order.
Finally, it should make the normalization of the electric motor (M2 / 4) with the reader STAR DIAGNOSIS, - ask for help from the service station Mercedes-Benz.