Tachometer Issue
 

Tachometer on 1990 ZR1 quits once in a while when driving.
Needle drops as if ignition key is turned off to less than zero.
If I turn the ignition key on (engine off) the tachometer needle does not go up to zero like normal indicating a bad connection.

Seems like a bad connector on instrument cluster since the tachometer function often returns to normal zero when ignition key is turned on and tachometer will then function normally for a while.

Re: Tachometer Issue
 

I had a crazy tach needle it was reading about half what It should have. decided to get the Batee chip and fixed it.

But you could for sure have some weak solder joints