Interior Dimmer Switch
 

So I went to cycle through the 3 settings (or however many it is) on my 06 MCa the other day....but nothing happens. The lights come on appropriately at night and everything, but the adjustment is not working. What should I be looking for?

Do you mean the dimmer switch to the left of the Speedo/Nav/Chrono? It's for dash/instrument brightness. Press and hold to brighten; press and release quickly to dim one step. See your Owner's Manual.

It has a lot more than three settings. Try hitting it a few more times.

The problem is I am hitting it and nothing's happening...I'm wondering where I should look for a problem.

Assuming that your dash gauges otherwise light up normally, all I could suggest is that your dimmer button (or connection to it) is malfunctioning. The button itself does not directly control the brightness. It sends signals to the BC1 computer, which changes the levels. If it isn't the button itself, the dealer will probably have to get involved.

Any new information on this topic?