I'm installing an OE tach in the dash of a '69 where a fuel gauge once was. The new OE tach as 3 terminals: 12volts, grd, and an unknown. I have no instructions to follow. I have not found a wiring diagram for a factory installed tach. All the diagrams I have are for a fuel gauge in that location.

Any helpful hints?

Thanks,

Other wire should be your signal from the neg side post of the coil. Or if your using a MSD box it will be the tach signal.

correct.... it should be a green signal wire you will need to run it yourself since this was a nontach car

Thanks for the info. The car I'm dealing with has butchered dash and wiring. I'm removing Moon electric speedo and tach (old hot road style black face) and going back to OE. There are at least 8 wires running thru the speedo hole in the firewall. The cluster housing was hacked up to put the Moon gauges in and the Pioneer stereo did a number on the radio opening. A fine winter project in deed!

When viewed from the rear the top left terminal says IGN which goes to the switched ignition terminal on your fuse box, usually a pink wire. The lower terminal is GRND which is of course is a black wire which goes to any good ground and the top right is TACH which is usually a brown wire which goes thru the firewall to the negative post on your coil. All the repro houses, Classic Ind's, Ricks First Gen and DR Classic, sell a tach harness, about $20, or make your own with female crimp on terminals. Now are you gonna run a center fuel gauge or a console mounted fuel gauge?
Ricks First Gen probably has the most accurate looking center fuel gauge, all you need are the posts or terminal ends from your old fuel gauge and the original plug will work!!
Check this link, if you can't click on it, copy and paste to the URL window:

http://www.camaros.net/forums/showthread.php?t=48391

You can use the back of the tach to make a paper template to mark the cut out if you don't have one, good luck!! I have pictures of dash cut outs so you get the right idea if you need to see one. Just PM me.

I plan to use the console gauge setup since there are also ugly Moon gauges there. All thoses gauges have also been spliced into the under dash harness with twist ties. What a mess!

Tach Template
http://69camaro.nextmill.net/temp/tach_template.jpg

Fred,
The thread I posted the link to provides good info for cutting out your dash center section if your installing the center clock to go with the tach and gauge setup. You should be able to find an aftermarket harness to power and light it or just make your own. Good luck.