How to calibrate the tac??

[bobbyhi]

Originally Posted by XfireZ51

The issue with our tach, like all the other electronic tachs since at least 84 is that the damn thing is slow to react. Get a shift light.

On my '90 the tach is also off by about 10%. I was thinking of just putting on a tach with the shift light and not worry about fixing the console tach.

[Jarek5_7]

guys do you know how the console tach is connected?

I dont think it reads the impulses from ecm because ECM reads good rpms. I checked it today with aldl cavble and datamaster. adn the tach shows almost exacly the twice rpm as shown on datamaster.

so I thought maybe tach is connected to coil or coils and there is somewhere a short and tach reads impulses from two coils instead of one or something like that.

[WVZR-1]

Rest assured that the error you're seeing is from "failed/failing" resistors/capacitors on the instrument cluster "main-board". Your confirmation is the "correct" output from the ALDL with your software.

Your location certainly doesn't offer a very economical solution to your situation. If you've an acquaintance here in the US you could arrange the repair from a facility here.

The error you see I'm sure has increased over time. Minimal error when you first noticed or suspected it and it WILL become worse over time.

[Jarek5_7]

I think I`ll get aftermarket tach and connect it on the electronic ingnition diagnostic terminal F, book says its instrument cluster tach input so then I will see if its the problem with instrument cluster or some wiring.