Philip A replied:

I am not a tech but have changed over a few alternators.
The B+ will always be the thick wire, so that is easy.
There are two basic types of alternator, machine sensed with only two main wires and battery sensed with three wires.

So the third wire could be either a battery sensing wire or a wire to a tacho from the S terminal. So does the donor car 12HT have a tacho?

I have never seen an alternator with an earth wire. The alternator earths to the engine by its mounts.

To find which is the wire for the light in the plug going to the old external regulator, put a volt meter to earth on both the small wires with ign off. If it is a battery sensing wire, one will be live when ign off and on.
The ign light wire will only be active when ign on .
A tacho wire will have no power at any time. Does an 84 FJ40 have a tacho?

On the alternator, are there B+ , etc marked on the terminals that the wires connect to before the plug? I presume there is a tail on the connector as you have given wire colours,. The light should be also B. And the tacho S.
Hope this helps.
Regards Philip A

Royston replied:

Hi Philip.

Many thanks for the great feedback. In this case all three wires (blue, pink,white) out of the back of the 2H alternator are the same diameter. They come straight out with no identification marks that I can see, and then feed into the green connector on top of the alternator. I suppose that makes it a battery sensing alternator. There is also no tacho in the FJ40. I think I might have to disregard the original alternator wiring and run fresh wires - and that's OK. I've already put a charge indicator light in the dash and run the wire out to the alternator. All that remains is to identify which wire goes where into the alternator. Unfortunately my HJ60/61 manual doesn't give me the colour codes for this late 2H alternator.

Thanks
Royston