Combo switch failure on the W210 is pretty common.

Which ever way this turns out for you, just be forewarned that if you do end up replacing the combo switch yourself (pretty easy job) be sure you disconnect the battery before performing the work, and ABSOLUTELY DO NOT re-connect it until you are 100% finished with the job.

I hooked my battery up midway through the job in order to help position the telescoping column, and unknowingly activated the SRS light (battery connected + no airbag present = SRS light). Only a dealer or an indy with the expensive computer can reset that light. OBDII scanner won't do it.

I figure I could save you a hundred bucks if you end up going that route...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280