Adding a tach to a '73 Mach 1

[Gud T.B. Blown]

Swapping a clock with a Tach in a '73 Mach 1

i have a '73 mach 1 and i'm in a bit of a quandry. the car came with a clock in the instrument panel and the p/o changed it to a tach, without bothering to hook it up. i've since wired it in but of course the printed circuit doesn't fit well and it doesn't light up, mainly because the printed circuit is aready in poor shape and needs to be replaced. i've thought of getting a tach cluster with the correct printed circuit but that brings the other problem in that the wiring harness plug from my car won't plug into the back of the tach cluster, the plugs are different sizes and different numbers of pins.
so as i see it i have two options:
1. keep it as is and get a new clock printed circuit and live with it.
2. get a tach cluster and try to find a tach wiring harness with the correct plug and integrate it with my current harness. and that brings up the question: is that even feasable.

any help would be much appreciated.

 

[mudbilly]

keep the tach

i bought a used tach/speedo cluster and plan on installing it using this for the wiring.. hopefully before spring.....i don't have the correct connector but will figure out some way of getting to those pins on the back of the tach

let me know if you get there before i do , good luck

By Rich Pajzer
Edited by Steve LaRiviere

Tachometer

To install the Tach in a car that didn't come with them, first purchase a used
speedometer/tachometer assembly.

You will need the wire connecter that goes on the back of this one, as it's
different than the connecter that will be in the car now.

Cut off the old wire connecter, and solder the new connecter in place by
matching the color codes of the wires. You will have a few wires left over,
just tape them up, they were for the idiot {warning} lights.

Next, at the fuse block, locate the red wire w/light green stripe and tap into
it with a wire. Run this wire to the male prong on the tach.

At the ignition switch, you will find two red wires w/light green stripes that
are together.

Cut both of them. One of these wires runs to the positive side of the coil. This
"Coil Wire" is the wire you want to locate. You will need to use an ohm-meter to check for continuity to the positive coil wire to find out the correct r/g wire to use.

Once you have the correct wire, connect this to the female prong on the
tach. (This "correct wire" is the "Resistance Wire".) Solder the other cut r/g
wire back to the ignition switch where it was cut. That's it!

P.S. If the car dosn't run, it could mean that the Tach was bad, as the power to the coil has to go through the tach, before it reaches the coil. If this happens, just un-plug the Tach, and jump the two wires together so that the car will run.

{Also on the tach where I say to cut the 2 wires, and then use an ohm-meter to locate the correct wire........you really don't need to use the meter.

All you need to do is have the car running...cut each of the 2 wires , one at a time , until the car dies. When the car dies, you have located the correct wire.

Connect the other cut wire, if it was already cut. (This should be easier, if
someone dosen't have an ohm-meter)

 

[Gud T.B. Blown]

You will need the wire connecter that goes on the back of this one, as it's
different than the connecter that will be in the car now.

this is the biggest hurdle to overcome. on ebay, tach wiring harness' are going for $200+ dollars. if you know if a cheaper source i'm all ears.

 

[HHStang]

I believe the Rich Paizers instructions above hardwire this in so the tach wiring harness is not necassary.

 

[Gud T.B. Blown]

I believe the Rich Paizers instructions above hardwire this in so the tach wiring harness is not necassary.

it's not the tach harness that is the problem. it's that the harness connector is two different sizes for the the tach cluster and the clock cluster. you can't just plug and play. i already have the tach hardwired and operational. the problem is that the printed circuit for the clock is different than the printed circuit for the tach, it doesn't line up. i would like my entire dash to light up at night.

 

[pshadwick]

If you can get the correct size connector you can pop the wires out of the old plug and push them into the new one. There are a cople of wires left over to run the idiot light that you now wont have. You can redirect these to the center gauges if you also out them in.
Sorry I dont know where to get the plug, I was luck, it came with the tack I bought.

 

[Gud T.B. Blown]

If you can get the correct size connector you can pop the wires out of the old plug and push them into the new one. There are a cople of wires left over to run the idiot light that you now wont have. You can redirect these to the center gauges if you also out them in.
Sorry I dont know where to get the plug, I was luck, it came with the tack I bought.

i understand about having to change the wiring if i change connectors. the intial question was one of trying to find the correct harness or living with the situation as it is.
luckily i found an underdash wiring harness relatively cheap so the issue solved itself, thanks.

 

[mudbilly]

luckily i found an underdash wiring harness relatively cheap so the issue solved itself, thanks.

may ask where and how much $$$ ?????????

 

[Gud T.B. Blown]

may ask where and how much $$$ ?????????

on ebay for $100. that guy listed it as mustang wiring harness. luckily i asked if the mustang came with a tach. last tach harness i saw on ebay went for $300. the harness also came with the center stack and gauges which i can re-sell for at least $50.