Anybody have experience with a tach problem. I have a 1990 740GLE, standard coil ignition system, and my tach quit working. I substituted another instrument cluster, but that didn't help. Any ideas what to do next. Book seems to show wire goes directly from coil to the tach, but that doesn't seem to be the case..TIA...

 

every electrical component needs power, a resistive element (in this case a tach) and a ground return. If any of the three is missing the device will not work. Run another wire from the coil just to test. I wonder where the ground return for the tach is?