we need to figure out how to fix/recalibrate our stock tachs.
this is fuggin ridiculous... my stock tach is so far off that its crazy!


anyone have a circuit of the tach internals, or know how its suppose to work?

i have a tach signal generator i made to calibrate and test my digital all-in-one gauge... and enough freetime on my hands, but if i could get a head start, that would be great......

 

well i agree with you about needing to figure out whats up with the tachs, I unfortunately dont ahve any time or diagrams

-steve

 

i could make the time if i could get some schematics..

 

This is a basic tachometer schematic:

 

The '90-'92 tach circuit also includes an integrated circuit board which plugs into the instrument panel carrier,and I believe this is the problem. I have two 1990 IROCs and neither tach reads anywhere near correct, but a scan tool will show the correct RPM.

I took it to the local AC Delco authorized "repair" center, and they just laughed at me.

I am sure this problem frustrates many members, any suggestions?

 

The most common thing to fail are the electrolytic capacitors. They change value with age causing the tach to read incorrectly. replace all the polarized capacitors with the EXACT value, most times that solves the problem.