Ok , so I'm cruising along at whatever rpm and Wham! to tach decides to peg. Quite unnerving. A slight thump on the tachs face plate and it drops back to correct rpms. All the connections at the tach seem secure. Any ideas???
sure sounds like the obvious....bad tach. check the connections at the engine as well. I would also be sure the tach has a good ground. Probably wouldn't hurt to run a temporary external ground to see if the problem leaves. Bad grounds are often the cause of odd electrical entities.
i have a force 90 hp and had an eratic tach problem due to a bad connection in the wire harness, the plug connector in the engine comparment (near the starter motor) was loose and would cause the tach to go nuts....but if your problems goes away by tapping on the glass it might be something else.
