Tach wiring help?

[jayoldschool]

I've been looking for inexpensive tach for my truck that would look old. I've found a few Mercruiser tachs that were used on Chevy 6 cylinder engines. Rev range is perfect for a stock 230.

Can anyone tell me how to wire this? Does it just need 12V and coil, or one of the senders?

[1963c-10]

Pink wire to ignition
Gray wire to dash lights
Brown wire to neg - side of coil
Pink wire to pos + side of gauge.
Brown wire to - side of gauge.

In your case it looks like you have a black wire for the light and not grey which would have been factory color.

Also.....HEI or coil?

[1963c-10]

Also....great thread here....go to tech articles.....install tach 64-66
http://www.earlyclassic.com/tech.aspx?category=Install Tach 64-66 Chevy3

[aerotruk63]

The black top wire is for a light is it not?
Red terminal to the + of the coil.
It looks like you would not need a sender unit.
Do you have a Chevy or GMC?
On Chevrolet it went through a grommet along with the windshield washer hoses?
Did I remember correctly?

[jayoldschool]

I have a Chevy 230. Original points.

That black wire at top is coming out of the light housing, for sure.

[markeb01]

The following link is the closest I can find to your exact tachometer:

http://www.classicglastron.com/phpbb...pic.php?t=7376

Also, blowing the photo up 400% and sharpening the image a bit, it appears there are very faint + and - marks indicating the post orientations in the original 2nd photo:



It also appears this unit was manufactured by AC Delco. There are a few pictures of them on Google Images.

[jayoldschool]

Thanks. Great detective work! For 20 bucks, I think I'll give it a shot.

[markeb01]

Correction - I found another similar tach on Images, and it clearly shows the upper center stud being the 12v connection (as does yours). This means one of the lower studs is for ground, and the other is for the signal wire, not 12 volts positive. Unfortunately I can't detect any markings on this other tach even under extreme magnification, so I would suggest doing low voltage testing of the gauge to determine which is the correct post before "going live":

[WOLFMANmike]

i agree with Markeb ^^^^^^^^^^^^

[1963c-10]

Have you taken the mounting bracket off to see if theres any id there?

I definitely agree the red post should be the pos

[jayoldschool]

Maybe... 12V+ on the red post (and the light lead), coil+ on the + post, ground on the - post... just thinking out loud.