I have a 1990 300SEL and yesterday my gauges stopped working. This includes the odometer, speedometer, tach, oil, temperature, and gas gauge. Is this caused by a bad relay or a fuse? One relay 201 821 00 47 is vibrating and humming, which I don't think is right. What caused my gauges to stop working? Help.

Problem fixed. It was the fuse. I had check all the fuses visually, but you have to take each one out. The top of number 6 was corroded. The problem would not have been found without taking out each fuse. The humming, vibrating relay box was misleading, but not the problem.

see above