Do you perhaps have an airvent that pushed into the dashboard? That's the spring that goes at the back of the chrome ring of one of the airvents. From the front, you have the chrome ring, dashboard, wavy spring and then the actual airvent housing, into which the ventilation pipe presses onto. Glad I could help

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Edit to add: No 41 on this diagram -
http://www.neoriginal.ru/cat/mb/part...033_/83_165__2