Topic: 1970 Alternator Wires

[1970 Snake]

I have a couple of questions regarding this harness, first can anyone advise exactly what connects to the blue connector part way along the alternator/regulator wiring harness, what connects to the black/yellow and what connects to the green, and is there a harness that connects to the blue plug? Secondly, all the reproduction harnesses have this connector in blue, but my original is black, please advise why?

[midlife]

All 1970 underdash harnesses I've seen (~200 so far) have that connector as blue.  It often gets discolored with dirt/grease, so if you clean it well, it will show a faded blue, but not as bright as the reproduction mating plug.

[1970 Snake]

Not sure what you mean by underdash? this is the alternator harness and mine is definitely black NOT blue.
Can you advise if there is a wire harness that goes from the brake booster area and runs along the bottom of the PS shock tower brace and connects in the solenoid area??
Do you know if this is the harness that connects to the blue (black) connector on the alternator harness?

[midlife]

That looks to be the correct mate to a blue, covered, molded connector that comes from the harness through a firewall grommet, routes along the PS firewall support bracket and goes to the starter solenoid.  That is actually part of the underdash harness; 1970 is the only year that the underdash harness doesn't end just past the firewall with a set of molded connector plugs, but extends the main power feed, alternator feed, and I and S 90* terminals from that point.  Every other year (well, 67-69), those leads are part of the headlight harness. 

So...it could be that your alternator harness is correct (I won't vouch for that as I don't refurbish them), but that black 2 pin (3 wire) plug appears to mate with the blue plug I described earlier.  The reproduction has that color for the mate on the alternator harness.

[1970 Snake]

Midlife, thanks for the detailed explanation, it is clear to me now where and how the harnesses connect. My through firewall harness like you said goes all the way to the solenoid and plugs on to the solenoid and the alternator to regulator harness. So to be clear you are saying the repop alternator to regulator harness is incorrect having a blue two prong plug, and I agree as I indicated my original is black, and as hard as I am trying I can not see even a hint of blue in the two prong matching plug on the through firewall harness it connects too. I have attached a picture of mine to show what I am finding regarding the black plug.

[midlife]

Midlife, thanks for the detailed explanation, it is clear to me now where and how the harnesses connect. My through firewall harness like you said goes all the way to the solenoid and plugs on to the solenoid and the alternator to regulator harness. So to be clear you are saying the repop alternator to regulator harness is incorrect having a blue two prong plug, and I agree as I indicated my original is black, and as hard as I am trying I can not see even a hint of blue in the two prong matching plug on the through firewall harness it connects too. I have attached a picture of mine to show what I am finding regarding the black plug.

No, the repro is correct as to color of that plug.  I've never seen a black plug like your picture before: they all have been blue or at least a dull gray (most are dirty/covered in grease). 
Take some lacquer thinner and clean your underdash alternator plug and see if it changes color from black to a bluish color.

[1970 Snake]

Well I have tired the lacquer thinner as you suggested and no amount of lacquer thinner is going to turn that plug blue, its black.

[midlife]

It's probably due to a different OEM manufacturer, as my best guess.