fbekholden.com

Hi Folks,
Got an old Stewart Warner tacho that I want to install. I am unable to locate a wiring diagram for something of this age so calling on others to see if I am on the right track?

In the picture (how it came) I have marked up the blue wire for tacho backlight feed and the earth (two wires already joined). Backlight confirmed it works. Presumably the other wire (red sleeved wire) goes to the coil wire that goes to dizzy. That wire would get 12 volt (positive) when points open then negative when points closed, creating the pulse.

Most of what I have found mentions a separate 12v feed. I don’t want to damage it. Appreciate your input.
Regards
Stephen

Hi Stephen,
I reckon green wire to coil negative, red to ignition power (coil positive), black to good engine earth.


FB ute fixer upper, EK van on rotisserie

Try this.

Make sure the little selector switch on the back is set to "8". For the first 10 minutes or so you can pretend that you have a high RPM speedway engine. Then set it back to "6".

... not that I ever did that

Cheers,
Harv

Thanks guys. A little more digging required I think.

Stephen

I reckon Clay has it nailed

Thanks Blacky

Moment of truth when you turn the key......

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I suggest that the green and black are the power for the light and the tach power joined together as if who ever wired it up last just had the back lighting on with ignition.. maybe …I would lose all the tape and check weather the colour coding has been changed anywhere under that tape..





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Good call Gledge
A previous repair

Couple more pics inside. The blue & green wires for the Edison screw globe holder are insulated from the rest of the unit as board is similar to Bakelite. Ohm meter confirms same. Only leaves red and black.


Thinking two joined with circular terminal earth, blue to dash light and red single to dizzy side of coil???

Try again

So green and blue are to the light and red and black to the mechanism ???

Yes Blacky

May have to work this problem by finding the model number then a specific wiring diagram.

Prior to 1994, the model and date code was stamped on the body of the gauge e.g:
970B M8
970B is the part number and M8 is the date code (August 1968).

After 1994, a 4-digit code was printed on the label, usually perpendicular to the part number e.g.:
0206
The first 2 digits are the year, 2002. The second 2 digits are the month, June.

As a fall-back, contact SW directly:
https://www.stewartwarner.com/contact-us/

Cheers,
Harv