Before you do too much -- change the fuse. I do not know why whith the gauges but I have had this very problem a few times and it was the fuse.

It is a good idea to change all the fuses -- MB says 10years for the type in the 107.

I have always thought that the fuses MB used are junk -- nothing but problems. They should have changed to the more modern units back in the 60's.

You need to also clean off the terminals -- not too much -- just get them clean and fit the new fuse - move it a little bit to seat it.