New Atlternator installed-still not charging

[Bikemanbrent]

vehicle is an '89 hilux surf, engine is 2lt 2.4 l diesel.
Alternator shop said my alternator diode pack was bad. They could not source one to replace and they did not have a replacement atlernator. Im in Canada and the Hilux was not sold here, nor the 4runner with the 2lt.
Yesterday I installed a new alternator I bought and shipped from australia. New batteries, new belts etc...
Charge indicator light is on and a voltmeter shows 12v at the battery which confirms the charging system has a fault somewhere.
So aside from a damaged wire somewhere does anyone have any suggestions what I should check next to find the cause?
Fuses all seem to be intact.

[Bikemanbrent]

i traced wires from the fuse block to ait wiring harness, found one bad wire , fixed it still not charging. A real head scratcher.

[Bikemanbrent]

voltage at the three prong plug with the ign turned to ON is on all leads, Ig, L and S is all showing 12v - battery voltage.
voltage at the alt with engine running @ 20000rpm is still 12v and the battery dash light is lit showing not charging.
Fuses all good.
my understanding was only the IGN prong on the plug was supposed to show 12v and the L and S lead should not show any voltage. at least from the diagram here
https://hiluxsurf.co.uk/manuals/vehi...i/charging.pdf
Not the same plug as mine but I figured out which was the L,S and IGN.
Any thoughts

[Bikemanbrent]

just to add, my ALT in internally regulated, no external regulator mounted under the hood or Bonnet as they say outside of north america.

[Bikemanbrent]

update , took my new alternator to a shop and had it bench tested , it checks out at A-ok.
So hunting for wiring and still coming up with nothing, Power at the alt plug checks out as good IG, S and L all seem to be doing what they are supposed to do. Cant find a bad fuse or wire from power or continuity test.
Any thoughts or ideas?