'83 300SD - What are these three black wires behind my gauges?
 

I just pulled the instrument cluster out for the first time, and there are three black wires which are connected to one common connector, which is pin shaped, about 15-20mm long, and not insulated. The wires appear to go into the console or possibly the air vents above the console. The connector was not plugged in, and I don't see an obvious receptacle for them. I'm guessing they power the lights for the upper bank of switches on the console, since they don't work.

Also, I pulled the cluster to investigate a non working tach and clock. I see a loom with two wires in it that have been taped off. One is black with a red stripe and the other is green with a black stripe. Nothing was plugged into the three prong receptacle on the right side of the cluster (directly behind the tach). Regarding the tach, I have already tried three different sending units (or whatever that round thing with the screw on cover is called on the driver's side of the engine compartment).

Not having a clue what car this is.....

I'd guess the three black wires are part of the fibre optic system for dash lighting.

Jim

sorry, just realized my mistake. it's an '83 300SD.

The item on the front fender is the tach amp.

Sometimes it can be brought back to life by inserting a foam peanut or a cigarette but under the cap to apply pressure to the integrated circuit.

Get yourself a MB repair CD with the wiring diagrams for info which wires are which.

It sounds like your tach has been disconnected behind the instrument cluster...

Jim