Yeah I had this same problem. Visual headlight blink was messed up and I had high beams on all the time and no fogs. I fixed it for free. It was a worn out combo switch stalk. I took it to bits and used some small screws to replace the four rivets.
Got a 1985 300D turbo
Post #72
The bad news is cleaning didn’t help. It had to be comepletely disassembled.
There is this plastic mushroom shaped piece that gets worn short. I grew it longer by heating it with a heat gun or a lighter and smushing it with a pair of pliers.
The end gets worn at kind of an angle and it stops working. I think my car was owned by somebody who enjoyed high beaming people.
My feeling was the OE stalk looked a heck of a lot better than the aftermarket ones. And if I’m going to be using that control a lot, I want a very good one.
It was time consuming to take apart and I had to keep the parts carefully organized with digital photos. But in the end it was pretty satisfying to get it working.
Good luck.