"Tach Suck"

I guess after 37 years you have to expect that certain delicate mechanical and electrical components have to start failing. The tachometer in the 240z is evidently one of the more common ones.

From Z

I suffered from "Tach Suck" which is more commonly referred to as, a Sucky Tach.

The needle on my gauge face would stick in random places in the lower RPM range of the face. Sometimes it would rise to 3 grand and stay there, other times it would stick around 1.5k and flutter helplessly in between. I thought sure it had to be getting intermittent signals from the sensor (which as it turns out doesn't even exist lol). The tachometer gets its signal from the ignition coil.

In the same thread that somebody chimed in to help me with my headlight issue, another noble HybridZ member pointed out the cause of my tach issue. The gauge was having a mechanical failure.

So I reached up into the dash from underneath the steering wheel and unscrewed the two Wing nuts holding the tach in place.

From Z

There were four light bulbs in the back of the unit. Two for illumination at night, and two for turn signals.

From Z

There were only four small silver screws holding the assembly together.

From Z

Two more silver screws in the back to remove and three wire terminals.

From Z

After flicking the gauge needle back and forth, redlining the fucker to 10 grand over and over again, I noticed that the needle would only stop at the lower RPMs when the gauge face was flexed just right. If flexed in the opposite direction, it almost always returned back to 0.

From Z

So in my limitless ingenuity (lol) I jammed a couple of washers in to hold the face just right and slapped the bitch back together!

From Z

Back together and the needle is flying free!

From Z

Thanks for the tip Zmanco! Much appreciated.