I finally got my harness all thinned for a swap into my 87 car and realized everything is there but anything having to do with the charging, oddly enough I cannot find a diagram anywhere on google, and nothing on my ecu pinout is relevant. Can anyone help??, I have the the alternator pigtail and such from another harness to wire in

It's pretty standard depending on how many wires are in the plug.

One of them goes to the fuse box to act as the field exciter, the other to the charge light in the dash. I don't recall exactly what the third wire is for on the later alternators, but it seems to me that it went to the fuse box as well.

 

These wires are not part of the main engine /ECU harness and are probably still hooked up where they need to be in the car, unless you pulled them out. All of them run from the general area of the fuse box behind the battery, across the AC compressor to the top of the alternator.

You should be able to trace each wire to its source to determine where it needs to be hooked up in your swap. I would think the only one you need to worry about is the one for the light, since presumably you'll be carrying over the fuse panel from the swap car.

Edited August 23, 201312 yr by Fairtax4me

On two wire systems the wire going to the fuse panel is the battery voltage sense wire. The other wire going to the warning light and ignition power is for the exciter. 

 

The three wire designs has one going to the ECU which controls the exciter I believe.

I have a 3 wire One, from a ej22, one went to ecu I believe, and its not the case with the wrx. So does the field control run off the main fuse box voltage?

I think it is controlled by the ECU and the battery sense voltage comes from a fused circuit to the battery.

 

Apparantly just the STi uses the three wire system.

99 and later Impreza and Forester use a 3 wire type. 2000 and later legacy use a 3 wire. Not sure about the really new stuff.

So would the field exciter just be hooked to 12v too?

No, it ties to the ECU which controls the exciter, I believe anyways.