Tachometer

I have an early 260Z and my tach did the same thing, jumped to 8000rpm with ignition on. However, the PO made a short in the circuit when wiring in a start switch (to fix the solenoid click, no start issue). After I removed the switch and reconnected the old wiring the tach would work intermittently, sometimes I'd have to tap on the housing. Then it pretty much stopped working so I figured something got fried inside. I took it apart and looked at it, no multimeter involved, and noticed nothing that would indicate damage. Just got a 280Z tach off of ebay so I'm hoping that solves my problem.

I put the 280Z tach in the other day and I finally have a properly functioning tach for the cost of $25.