I had the same problem on my 91 190e and it turned out to be the fuse.
The fuse would look ok upon inspection but when I swapped it, all the gauges work.
The fuses on my car are of the ceramic type and are known for this problem.
Not sure on the type of fuses installed in your car but it's a cheap fix to try. Give it a shot!
1991 190e 1.8