I also believe there is a separate strip fuse aside from the fuse in the fuse box. It's a 30A. If the design is anything like the 1991 420SEL that I worked on that had the same problem, it might be that fuse. It was located in a little 1"x2" plastic box just infront of the main fuse box. When you open this little box, there are two hold down screws for the fuse. I would double check this fuse and the fuse in the main fuse box before looking at anything in the dash.