Posted on August 10th, 2011
Hidden in the dash of that nice C-Class are a series of small plastic levers, which, given time and use, may fracture, resulting in an unusual noise from the dash area. The noise is noted as a “snapping” or “popping” sound in or near the center vents, and the customer may also have a concern about incorrect temp or air flow from the vents. The problem, a small plastic lever which operates the foot well flaps via a servo motor. In this car, we found both the broken link as well as a defective servo motor. The servo motor had a damaged internal gear, but was not on the flap link which had broken, but rather was on a air direction flap on the passenger side.
Running a diagnostic with the Mercedes SDS computer should confirm the fault, before the teardown and visual inspection. The plastic lever in question has been redesigned to be more robust, and the update kit is available from Mercedes. The service correction is quite involved, requiring removal of the center console upper panel, radio, climate control head, and lover dash with the glove box. Once the arm is located and replaced, the SDS should be used to run a “normalization” routine on the flap system.