In Reply to: Not exactly posted by Nicholas on April 03, 2000 at 02:13:46:
: : The tach is fed through the S.I. board, so an S.I. board problem can make the tach inop. Does your OBC not light up, or not function at all? My OBC continued to function after the S.I. board wiped out, but the tach quit. I think it's possible to lose some OBC funtions related to fuel consumption if the S.I. board quits, but I'm not absolutely sure about that. If the OBC is not lighting up, then you probably need the $20 light bulb. Hope this helps.
In my '89 M3 (euro spec) I have occasionaly the same problem. When I pass over a bump, sometimes the OBC and the tach goes off. In the next bump they usualy return to normal function.
I think that the cause for this is some bad electrical conection in the dash board, but I didn't have time to check it.