BMW: coolant temp gauge inoperative, service interval, euro spec

Question
I have a euro spec 1984 323i (E30) with the 2.3 6 cylinder. the temp gauge has stopped working, and I have had little luck tracing the source of the problem. I have gone as far as checking ground to the cluster...it's okay. But my service interval indicator has stopped working at about the same time as the gauge stopped. Could this be related?

Answer
Fritz,
 If I remember correctly My car did the exact same thing. the coolant gauge stopped working as soon as the lights went out on my service indicator.

 Usually this is due to the batteries finally going bad on the service indicator.  If you can solder wires together you can fix this yourself as I did.

 Here's a do-it-yourself link to fixing the problem:
http://www.bmwe30.net/cgi-bin/datacgi/database.cgi?file=articles&report=view&ID=...