68 GTO Dash Tach
 

I just purchased a 68 GTO. The tach is not hooked up. My problem is I don't know what type it is. I know the prown wire is for the tach. It is there. The tach has three terminals. Someone labled them: 12v, negative , grd. In all the books I look at there is only one terminal for the brown wire. What do I have. It looks original and is a 5100 redline.

Sounds like someone has replaced the original meter movement and circuit with an aftermarket tach unit.

Exactly what I'm planning for my tach, too.

Maybe 12v is + for the light, negative is for the coil, and Grd is the - for the light ? Not sure just guessing.

Can you take a picture of the back of the tach and post it?

Will do. Hope to have it posted this morning.

pictures
 

Here is the pictures of my tach.

I'm sticking with my reply. The meters been changed over to a typical aftermarket tach movement.
The brown wire from your coil (-) goes to the terminal labeled negative coil.
Run a +12V ignition feed (hot with key on only) to the 12V terminal.
And run a good ground to the ground terminal.

That tach movement will work with points or GM HEI.

Ground goes to a good know ground, coil negative goes to coil negative and bat+ goes to a constant 12v source.

Is there a kit you can buy to change over to the new tach movement or do you have to buy the complete aftermarket tach and switch the internals?