Tach Wiring Help...and YES I searched !!

Need some help here folks...
I am trying to figure out how to wire a tach..
No name on it, but looks like out of the sixty's..and on the back says "Made in the USA"..
It has four wires coming out...I opened it up, and there is a green and black wire coming out of one area (I think the tach operation) and a yellow and blue wire coming out of what appears to be a light ?
I am thinking the green is hot and the black is ground for the tach??
Any help would be much appreciated.
Cheers,
Bob

 

that looks like a twin to the RAC tach that I have out in the file cabinet in the shed that has been on a number of my cars for the past 40 years.

If it's like mine there is a switch inside that switches it to 4-6-or 8 cylinders.

I don't think I tagged the wires on mine though so that idea is out.

I found this link that might be some help.
http://www.mombu.com/chevrolet/chevrolet/t-old-rac-tach-wiring-diagram-1712754.html

 

green to coil negative,black to ground,yellow to key power, blue to dash lights. thats how id do it.

 

The green goes to the coil (-)
Black to ground
One wire for (+) and one for the light
Hook up black to ground and see which wire lights the light
The other will be the (+) and probably make the needle bounce

EDIT: What he said^^^^^^^^^^^^^^sounds about right

 

Just gotta love this place....
Post a question, go into the kitchen and have a big bowl of chili, and come back to THREE replies...
Thanks a bunch guys!!
Cheers.........