I recently got an '81 380SLC that needs a few details. Most importantly, the speedometer/odometer (center part of the instrument cluster) do not work at any times. I put another instrument cluster from my old '84 380SL and it does not work either. I know the problem is not the cluster because of this. Is there any relay that controls it and where can I find it? Any other electronic parts that I need to compare with the parts of my '84? Speedo IS electric, not with the long analog cable from the tranny. I searched already and found only related topics, please help!