Tach Dash conversion - 94 GMC

[ChevyTech]

Originally Posted by HondaMartin

Do you know what wire it is for the tach? Im just adding a stand-alone tach and want to use the original wire. Is it the white wire coming from the distributor the nothing is plugged into?

My understanding is all the 1992 and later trucks had the wiring there for the tachometer and all you need to do the swap to a tachometer instrument panel.

Note: when buying an instrument panel make sure you buy one from a truck that has the same number of cylinders as your truck. There is a difference between a V6 tach instrument panel and a V8 tach instrument panel.

From the 1993 wiring schematic manual:
Circuit 121 is for the tachometer. The wire color is white.

Circuit 121 is in cavity “T” in the instrument panel connector.

There is a gap in the middle of the instrument panel connector. One end has seven cavities on each side and the other end has six cavities one each side. Cavity “T” is the closest cavity to the the center on the end with seven cavities. The wire color should be white.

The white wire by the coil with nothing plugged into it connects to the same circuit that goes up to the instrument panel tachometer.