Tach and clock not working?

[Bizarre]

So Im working on an e30 i just picked up. When I first got it the tach was dead. I assumed it was the si batteries since it seems to be pretty common. Well three clusters and replaced batteries later, I still have no tach. The weird thing is one day it decided to work perfectly fine and since then it never has? I've checked the obvious like the fuse and I've also replaced the clock b/c i thought it was just a dead lcd display but no dice. Im going to assume it's something to do with the power to the tach and the clock because from what I've read they get it from the same source. So where should I start to diagnose this? Obviously its not as simple as just throwing parts at it, im going to take a guess and say that theres some sort of break in a wire somewhere. Also the econometer doesn't function. Any help would be appreciated! Thanks!

[jlevie]

You could have a wiring problem. The best approach would be to use the wiring diagrams for the car (see http://wedophones.com/BMWManualsLead.htm) and see if/where you are loosing power to the cluster and clock.

[twright]

I fixed the tach in my 1991 318is by tightening the nut on the motor that drives the needle of the tach. This is not the nut on the back of the cluster. You have to take the back off of the cluster to get to this nut.

After I tightened it, it worked great.