Ignition Wire

1hotboss · Sep 13, 2016

Help needed. Removed my stock tach from my 71, and I have jumped the two wires to allow me to start the car and move it around. My problem now is where do I attach the red ignition wire from an aftermarket tach. The black wire from the tach is ground and the green wire goes to the negative side of the coil.

Please provide detailed suggestions....Newbee at work

Thanks

jbojo · Sep 13, 2016

At the point that you jumpered the 2 wires take a voltmeter and measure what you have there. If it is 12 volts at key on you can connect there.

midlife · Sep 13, 2016

Noooo! After market tachs take their signal not from the + side of the coil, but from the negative side of the coil. Your original Ford tach was wired to the + side of the coil because it is a current-sensing device; all aftermarket tachs are voltage sensing.

jbojo · Sep 14, 2016

Noooo! After market tachs take their signal not from the + side of the coil, but from the negative side of the coil. Your original Ford tach was wired to the + side of the coil because it is a current-sensing device; all aftermarket tachs are voltage sensing.

Midlife,

Isn't this correct:

Red is connected to +12V switched

Black to ground

Green to - side of the coil

He mentioned that the green wire was connected to the - side of the coil.

midlife · Sep 14, 2016

Yes, that is generally correct. Did I mis-interpret the post?

Ignition Wire

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Ignition Wire

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