Re: How-to: 1990 Ford Mustang 5.0l RPM tach.
Next I needed to figure out were to run the Tachs coil signal wire to. I pulled the coil cover off the vehcile and found the negative terminal located on the coil plug. For those who may not know, the negative coil wire is tan with a yellow stripe.
Now that I knew where everything would be wired, it was time to figure out where to mount the Tach. As most of you probably guessed, I mounted it on the dash just to the right of the drivers side cluster.
I then drilled a hole in the dash where all the wires would be run and installed a rubber grommet for a clean look.
After fishing all the wires down the drilled hole, I ran the Tachometer's SIGNAL COIL wire (green) through a boot under the driver side dash. Again using a T-Tap connector, I made the connection to the negative coil wire.
Now that the coil wire was taken care of, it was time to run the LIGHT (white), GROUND (black), and POWER (red) wires off the Tach into the radio compartment and make the necessary connections.
With everything connected, it was time to test functionality. Here's a quick video...
After a sigh of relief :) I put the radio back in and hid any exposed wires with black cable cover.
Here's the finished look.
Thanks to Matt over at Discount Tire Direct, For the great write up, and pic's.