Drop the kick panel above the drivers feet. Three screws accross the edge closest to the dash and a couple 1/4 turn screws on the right and left side. I've seen em mounted a couple different ways. The one in my 240D is mounted directly to the other side of the kick panel and the 300TD is mounted to the left of the steering column. It is a silver aluminum box about the side of a pack of cigs. You will be looking at the end of it as you look up into the bottom of the dash.

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Jim