Whatever dude, I've been a tech for 45 years now and worked on them when they were brand new and owned plenty over the years. What you just described sounds more like a bad ground. Which can burn out a fuse link. Something those old D and W series are famous for. Bob however is asking about a B van. Similar but different.
Ya know you don't have to thump your chest everytime someone disagrees with you Mr. Mercedes Parts Counter Man. Ok?
I'm not a tech and do not pretend to be one. The fact that I toss parts to techs means nothing in this situation.
I'm sure in your 45 years of fighting cars you've had some serious electrical head scratchers.
In my case, fixing grounds helped some of the issues but did not fix all of the issues. The weirdo malfunctions and mishaps went away when I removed the bundle of fusible links and replaced them with a maxi fuse block I scrounged from a Cadillac in the salvage yards.
Those old fusible links get the crusty green death over the years. Sometimes they carry current well, other times they don't. They looked fine from the outside but 27 years of life under the hood took a toll on them.
They may or may not have anything to do with the issue he's having but it's not going to hurt to check them for proper current capacity.
