3 Wire - 1 red , black , green or white !!!
Connected red to battery to test with green/ white to - post of coil , black to neg on battery . Turned on ignition and light lit but tach did not work !!!
From what I have researched when light is included it has a 4 wire system . This and old Dixico tach . Opened up the innards & looks to be all original with 3 resistors in tack and 3 wires going further inside with no sign of 4 wire or if it had been altered . I tried to connect it again and the truck would not turn off when I turned off ignition !!!!!!!!!! !
It is about to rain so I must git back outside to bring lots inside Back later..........

 

Sounds like the tach has aged out to me.
You are correct about the four wires, but in the old days I used to see quite a few tachometers that had the light turn on with the key. No separate circuit.
The tachs with separate circuits usually had a blue wire if I remember for the lamp circuit. But I would not rule out the fact that your tech may originally have only come with the three wires, and that’s just how it worked. And it also sounds like yours is defective.
Possibly why the PO sold it.

 

RTT, see attached. I used an old Autometer tach and found these instructions online. Hooked up as shown and everything works.

 

RTT,
In addition to what Eric Hamilton sent you, attached is instructions I received from Autometer for an old tach from the 80's. It may not apply to yours but sending it just in case it does. My tach had looped wires that were used to select the number of cylinders, as per the instuction sheet. Works fine on my 67 - 352 V8

 

Here is an actual Dixco tach instruction sheet:
https://board.moparts.org/ubbthreads...ixco-tach.html
https://www.jalopyjournal.com/forum/...wiring.685722/
Use red for 12v instead of the old black.

 

Thank-you all so very much !
My delayed response is due to I have been sick 16 days . I have either lasting affects from Covid or Flu . I cannot breath properly it is not major but I have almost constant slight burn in wind pipe & upper chest & loss of oxygen.......
I have not tested tach again , but will add I connected red wire to the battery which was probably wrong thing to do I may should have connected to fuse block or ignition switch . My logic was it would not get power unless coil fired but now that seems dumb !!!!!!!!
I do think I saw it try to work once .
DID I DESTROY it when I connected it straight to battery

 

How do I connect to the power terminal of distributor , per illustration ???
I have a Chrome bracket as in illustration , but DIFFERENT color wires --- One wire is either white with green rubbed off or green with white rubbed off AND a RED wire and a BLACK wire
I will look at GREEN/WHITE closer !!!
Black is IGNITION SWITCH !!!!!!!
I SEE NOW I got it mixed up with the POSITIVE GROUNDED BATTERY
BLACK is IGNITION SWITCH
So is GREEN/WHITE GROUND and
RED connect to PRIMARY DIST . TERMINAL , or the NEGATIVE side of COIL Which may be the PRIMARY DIST . TERMINAL

 

Very strange! Maybe they were just getting around to making the wiring more automobile-centric rather than continuing to use the household-centric coloring of White for ground (actually neutral) and Black for positive. And the packaging and instructions just had not yet quite caught up!

Never seen one connected to the distributor, even back when only points were used. Easier to connect to the coil, but maybe they figured the distributor was easier and more reliable a location?
But you're correct that the distributor is the same as the coil's negative terminal. Presumably this tach is so old that it did not even need to take electronic ignitions into account.
Do you have an electronic ignition of one type or another? I wonder if the coil simply won't work with this type of trigger.

Can't say that connecting it backwards would have killed it, but it might have.
And I'm at least assuming that it wasn't happy for a bit!

Paul

 

Paul , thanx 4 the reply..........I got an electronic module (Pertronix Dist. & Coil) .......You think RED is hot to coil or ground ??? I feel black is the hot 2 ignition per illustration
I gonna b signing off soon...........glad u responded...
Oh I think old distributors , some had a green wire hanging out.........if this matters here who knows.....

 

Pertronix uses the Red wire in it's more common position, as a switched 12v positive power source. The Black wire from the Ignitor goes directly to the ignition coil's negative side only.
In applications where there is no resistor, or (as in our Fords) a resistor wire, you can connect the Pertronix distributor's Red wire to the coil's positive side to get it's switched 12v source.
However, in the presence of a resistor, the Ignitors don't really like less than 12v to operate (they will sometimes, but they don't always like it!) you need to find a reliable source of the full 12v switched by the key. Preferably ONLY when the key is in the ON position and not when in the ACC position.

So I see it like this so far:
1. The distributor's Red wire to the 12v source from the key.
2. The distributor's Black wire to the coil negative.
3. The tach's Green signal wire to the coil's negative side.
4. The tach's Red wire to a switched ignition source. Can be the coil's positive side probably, but not sure.
5. The tach's Black wire to a good ground. This is NOT for the ignition coil's negative side, but for an actual permanent ground.

If the Black wire is under the dash, find a spot on the metal dash or firewall or tunnel or wherever it's convenient but out of the way, and connect it there.
If you do not have a good body ground at the battery and engine, now's the time to add them. Or put them back as the case may be.
A single 10ga wire from the battery negative to a body panel nearby is a start. But to me the key body ground is the one at the back of the engine to the firewall. This grounds the dash area cleanly and reduces radio noise and helps things like ignitions and dash lights and tachometers and such.

Paul