Author Topic: Tach VS non-Tach dash harness  (Read 347 times)

Offline Angela

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Tach VS non-Tach dash harness
« on: July 19, 2017, 11:12:53 AM »
Would anyone be able to educate me as to the differences between the non-tach and tach dash harness for 1970 (or 69)? I have a tach-dash 1970 car, but the dash harness had been sold before I purchased the car. My goal for this particular restoration is such that I'm not overly concerned about getting the dash harness perfectly correct. As such, if it's possible to relatively easily modify a (less expensive) non-tach dash harness so that it will function with my original tach cluster, I'd consider going that route.

I do know that the non-tach harness is missing one or two pins at the cluster connector. What I don't know is (a) where do those wires go and (b) is that the only difference compared to the tach-harness.

Thanks.

Offline midlife

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Re: Tach VS non-Tach dash harness
« Reply #1 on: July 19, 2017, 02:15:43 PM »
There are significant differences between tach and non-tach underdash harnesses, mostly related to the use of an ammeter vice an alternator indicator lamp.  The ammeter uses two lines directly from the headlight harness to go to the gauge.  The lamp system uses one line from the Voltage Regulator and compares that signal to a RUN-only line.  In addition there is a bypass resistor wire in the circuit such that if the lamp is broken, the voltage regulator will still get a signal that the key is in RUN position.

The routing of the pink resistor wire changes from one configuration to another.  The voltage regulator wiring on the headlight harness changes from 3 pins being used to 4 pins.  The circuit cards are different.

Basically, everything forward of the tail-light harness changes with the single exception of the engine gauge feed.

Offline 7Lscjracer

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Re: Tach VS non-Tach dash harness
« Reply #2 on: July 19, 2017, 10:27:51 PM »
They're about $800 on eBay for a 70 with tach harness by Alloy Metal.
A nice harness that will get the job done, but I doubt it would stand up to side by side comparison with an original.
I bought Alloy Metal courtesy lamp and door speaker harnesses for a 66, and LH and RH both had the same color speaker wires as a cost cutting measure I would say.
That's why original is still big $.
Hopefully your printed circuit is good because that's another expense you don't need.
You could get the cheaper Mr Mustang brand, but I wouldn't for a car you want to keep.
69 Mach 1 San Jose Nov. 68 build

Offline midlife

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Re: Tach VS non-Tach dash harness
« Reply #3 on: July 20, 2017, 07:37:16 AM »
I sell refurbished harnesses for $225 (standard) and $275 (tach), including a $50 core charge.  I only use original components.

Offline Coralsnake

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Re: Tach VS non-Tach dash harness
« Reply #4 on: July 20, 2017, 10:38:38 AM »
I shall give you another viewpoint...

How much is is your car worth? Do you think that this an area you want to use a less expensive part?

Based on the time it takes to replace a harness and its importance, I would argue you want the best possible part. The two harnesses (tach vs nontach) are fundamentally different. If you change the underdash, the headlight, the engine gauge feed and the alternator harnesses also need to be changed.




I would also disagree with the characterization that Alloy harness wont stand up to the original in appearance and function. The harnesses have been used by many Shelby show cars for decades. Ford literally made hundreds of thousands of Mustangs in 1970, not every harness was the same. Alloy harnesses are new, not brittle, same connectors, same gauge wires and almost always the same colors as OEM wires.

If you need more help, I can probably do better on the price than $800, but you still need to take the others into consideration. Just something to consider. In summary, dont try to do this on the cheap.

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« Last Edit: July 20, 2017, 11:02:20 AM by Coralsnake »