Tach?: 3.2 backdate

[chrisf]

looking for just a little additional info/confirmation on tach wiring issue:

1. installing a 3.2 into a '76. Using the original, rebuilt (by NHS! check out the pic below. This thing, as well as the rest of the gauges, is a work of art.) tach.




2. Have located the black/vio lead from the DME.

3. Have read in this very good mod thread Modification that this black/vio DME lead goes to the middle spade of the tach. For this mod thread, the author was installing his 3.2 into a '77, which I am assuming to be the same as my '76.

4. I have read (believe me, I have been using the "search" function for awhile this morning) that the tach signal is always driven by the black/vio lead.

So, it seemed like I had all the info I needed to proceed. Until I started reviewing all the pictures (not very good, I know) I took while disassembling the car. In some of the pics, I see that my black/vio lead was located on the end spade of the tach.



This spade is designated as “TD”. The middle and far end spade are label “+12V” & “-“.

So I did a little more searching and have found a few other conversion threads, and confirm the tach is driven by the black/vio wire. My pics were confirmed by a few other midyear pics from other pelicans:





My question is this: Should the original mod thread I referenced simply have stated that the black/vio DME lead goes to the spade on the tach that has the black/vio lead currently connected to it, i.e. the “TD” spade?
In addition, that mod thread states that the black/vio DME lead is “spliced”. I understand that he made a jumper (green wire, b/c the DME lead is probably too short). Does this mean that the black/vio DME lead should be spliced into the existing black/vio lead, and then onto the tach spade, Or does the existing black/vio lead need to be replaced with the new DME lead?

Thanks,

~Chris

[chrisf]

in that last sentence, maybe what I am asking is: "is there any reasons why the original black/vio tach lead needs to remain on the tack, or is the only black/vio lead needed to connect to the tach be the one coming from the DME?

(sneaky bump)

[chrisf]

bump still looking for a little confirmation on this.

~Chris

[timmy2]

The tach signal is coming from the DME, so swap it out with the existing one if it will reach.
Splicing may have been a wire length issue.
Tape off and label the old one.

[chrisf]

hey timmy2, thanks for the reply.

So, the the new lead coming from the black/vio DME wire, will go to the end spade on the tach, the one shown in the pictures with the black/vio wire?

[timmy2]

Originally Posted by chrisf

hey timmy2, thanks for the reply.

So, the the new lead coming from the black/vio DME wire, will go to the end spade on the tach, the one shown in the pictures with the black/vio wire?

Yes, Hopefully the '76 tach is compatible with the signal from the DME. It sounds like others have done the same swap so you should be ok.
If it doesn't work, try a 3.2 gauge.....

[baimasanji]

The tach signal is coming from the DME, so swap it out with the existing one if it will reach.