Dash Gauge Cluster PC plug PIN out for a 70 Mach with Factory Tach

[Rich Ackermann 174]

I have looked everywhere for a good (accurate) diagram of the Dash Gauge Cluster PC circuit board plug PIN out for a 70 Mach with Factory Tach with no luck. At least something that resembled what I have on my  70 Mach with Factory Tach. Soooo.... I decided to study the Ford electrical diagrams and compare it what I see on my car. The Ford diagrams are bit off with respect tot he various resistor wires for such things as the CVR, Alt warning light, and the tach (which BTW has nothing to do with the PC circuit board plug).  I believe I have it right and though I'd share it for anyone else that might find it helpful. I am sure Midlife or someone else will want to correct me and I welcome any corrections or comments.

BTW: The pictures of the plugs at the bottom are of my 70 Mach 1 with Tach. I did plagiarize someone else very nice diagram of the plug...I would credit them, but I don't know who to give credit to.

[Midlife 814]

Almost right.  Pin 7 is just the green/red wire.  The resistor wire goes from ignition switch to the green fuse box backing, where it is tied in with Pin 7.  The resistor wire starts at the ignition switch at the ACC pin or at the OEM splice above the ignition switch connector. 

However, what you have done or what you have is electrically the same. 

[Rich Ackermann 174]

3 hours ago, Midlife said:

Almost right.  Pin 7 is just the green/red wire.  The resistor wire goes from ignition switch to the green fuse box backing, where it is tied in with Pin 7.  The resistor wire starts at the ignition switch at the ACC pin or at the OEM splice above the ignition switch connector. 

However, what you have done or what you have is electrically the same. 

Thanks Midlife. I don't understand when you say "to the green fuse box backing, where it is tied in with Pin 7"?  

I went back and retraced the resistor wire in my harness. I think whoever made my harness deviated a little from the schematic and ran the resistor wire from the black/green striped wire at the ignition switch plug to pin 7 where it joined with the green/red striped wire also at pin 7. I have no Resistor wire anywhere in the fuse box.  I guess whoever that was also knew it was electrically the same.

You can see in the pics below the two wires in PIN 7 (my red and green wire colors are washed out in the pic) and also at the ignition plug. I'll note the deviation in the diagram and re-post it.

Thanks again!

[Midlife 814]

There's a violet resistor wire pinned with the black/green thick wire at the ignition plug: that is a 10 ohm resistor wire for the dash cluster constant voltage regulator. 

On the back of the fuse box is a square green plug with female pins: that is what I meant by the green fuse box backing.  If you measure resistance from pin 7 to the right pin on the green fuse box, you should see 15 ohms.  That pin is on the row below the big pin, and on the far side away from the big pin.

Your harness is wired a bit differently that what I typically see, but that may be due to a different vendor who manufactured it.  I know of at least 3 variants, mostly due to AC vs. non-AC heater box connector plug placement, powering door ajar relays, etc.