I would check voltage regulator (brushes). Should be about a $20 part -- $45-$50 for Bosch/MB. 2 screws and 8 minutes later and you are good -- and that's if you have to crawl under the car as I did on my W124.
My dash lights did not light with the key on position 2. They do again now.
This was on a car with 115k. I replaced the ones on my older car with 166k proactively. They were almost totally gone!
1986 300E Anthracite + ECodes + MB Mileage Award