Connecting my tach properly!?!?

[KamakSun]

Happy Saturday fellow nickel and dimers,

 

My tach has three wires going in.

 

The negative from the coil, this was easy

A positive

A ground

 

Two questions, should I run the positive off of the coil or a constant positive?

 

Where should I run my ground from?

 

Thank you,

Kamaksun

[Lockleaf]

Ground cable can go to any good body ground.

 

Power should be taken from something else that comes on when the key is in the ON position

[datzenmike]

The coil doesn't have exactly 12 volts on it when running anyway. More like 8 volts. Connect to the ignition switched side of the fuse box.

[erniestr8mingin]

Is there a specific wire on the interior harness that you can connect the negative coil wire to? Black/Red?

[datzenmike]

The '75 didn't have a tach option so there are no wires for one.

 

The negative coil wire is the signal to the tach, so just run a jumper from it into the cab through the hood release cable grommet.

[KamakSun]

How bout a 69? I have the factory dash and I don't see a tach but the center panel has been gutted

[datzenmike]

  Most white and orange needle factory tachs were of the inductive type. Only the '73 was wired in parallel with the coil.

 

If after market follow those instructions.

[rinigado]

ground somewhere there's a ground (a bolt/screw in the firewall, under the dash?). 12v from some accessory, just like the radio does; turns on and off with the key. signal wire just run another chunk of wire through the firewall to the coil.