I just fixed my odometer gear in my 86 745. However, occasionally the speedometer and odometer will both quit working. The speedo needle falls to zero and the odo quits turning. Sometimes the speedo needle will bounce back up on its own, but sometimes if I tap the plastic cover in front of it lightly it will begin working. How can I clean the contacts and other things to make sure this thing works better? Do the contacts with the screws acting as connections go bad? How do I clean that? I notice slight discoloration where the screws hold down the ribbon cabling on the back. I think since tapping it will get it to work that the sensor and wiring must be good, but I'm not sure. Ideas?
-Nathan

I had a similar problem in my 1991 740. The whole instrument cluster would go goofy so I yanked it out, resoldered every solder joint in sight, cleaned the contacts where the screws meet the ribbon cabling, and smeared conductive grease stuff all over the undersides of the screws. Oddly enough, it completely fixed it.

-Greg