help with wiring up 5 in. tach in my 90gt

you are on the right track.

black ground: i would have ust placed it inside the cockpit, but no biggie (i know the vendor sites say to use the battery).

green tach wire goes to the green (with some sort of stripe) wire on the coil (normally closest to the fender).

the red wire goes to a key-on hot source. there are yellow wires under the column which are key-on hot. i dont know about the wires you chose - they could work - just check them with a DMM first.

you could also tap off a key-on hot fuse in the box. for illumination, you can use fuse 13 - the ISO circuit. tap into the dead side (and use your own fuse on the white wire) and the tach will dim with the dimmer/stock gauges.

good luck and enjoy.

sounds good. there are several ways to do it (personal preference). i take it you have an Autometer tach?

depending upon the location of the tach, some use the HVAC lighting wires (part of the ISO circuit, IIRC). others dont want dimming and use one of the brown wires under the driver side dash (parking lights). some tap into the headlight switch wiring, as you describe (i find grabbing juice off fuse 13 easier). and so on. no one right way. you are on the right track - i just said how i might do it (or one option).

good luck.

look behind the radio and hook up there much easier if you have a harness for the factory radio plug the wires will be labled white will go to dimmer wire orange with black stripe