dead rev counter and temp guage

[biggee]

1987 e30 M3.The rev counter and fuel guage will not work.I have tightened the little earthing nut on the back of the rev counter but still no joy.There does not seem to be an appropriate relay specifically for these.Does anybody out there have any ideas.

Regards.

[Bruce]

SI board is bad...either the batteries or the board itself.