I searched around, didn't find quite what I was looking for, thought I'd just ask. I'm dealing with a funky gauge cluster in this '86 z28 I picked up. It is a 145mph unit in there.

Speedo/odo, volts, and oil pressure works fine. Fuel gauge is working, but bounces around erratically (more than normal) when driving - my guess is a failing sending unit.

The tach is the main issue, it's all the way to the right and bounces slightly to the left when you start up the car. Does not move when you rev the engine at all. The temp gauge also does not move and is stuck all the way up. The car runs and idles fine and does not seem to be running hot.

Looking for suggestions on how to diagnose the cluster and if it can be saved. I saw a thread about fixing inaccurate tachs in 90-92 clusters, would that same fix apply here? Thanks!

 

There's a high probability that the Tach is smoked and needs to be replaced. You can check the tach readings by 'tapping' into the Tachometer signal with a dwell meter. I would probe right at the distributor TACH output terminal.

The Temp gauge could be the gauge, the sending unit, or the wiring. If everything is working OK then,.... when you turn the key, un-plug the temp sensor and "jump" it to ground the TEMP gauge should shoot past the top of the scale. If that doesn't happen the problem is the cluster printed circuit, wiring, or the gauge itself is the cause. Next; pull the cluster and start checking plugs, see if the printed circuit is OK, and test the Temp gauge independent of the cluster.

 

OOPS

 

For the temp gauge, first try moving it back to 0 by hand with the ignition off.

The temp gauge goes to full hot when the wire is shorted. Check to be sure it's plugged in right. Driver's side head between #1 & #3 spark plugs.

 

You can repair your tach or have it repaired.
https://www.thirdgen.org/forums/engi...achometer.html

 

Sorry, I meant, for the tach, try moving it to 0.