rev counter help

[imye30]

the rev counter has a mind of its own while driving it goes up an down when at a steady speed an works some times

[eta]

Tach signal wire has an intermitant break in it. Trace the wire back from the cluster (or the problem may the plug at the back of the cluster) and find the break. Or clean up the contacts with of the plug at the back of the cluster with contact cleaner.