I had the same problem on my 99 S420. The sunshade just stayed in the up position. The fix was to change the entire sunshade assembly in the rear hat shelf. I hardly doubt it is the switch but if you want to test the switch: press it and pay attention if you hear any motor noises. I checked the fuse by having 1-800 for mercedes walking me through it. The service advisor said it was a very hard job and I woudnt attempt to fix it myself. I really doubt that it is the switch itself. I've never had any problems with Mercedes switches.