Ballast Resistor and Field Wiring Issues

[metallicareload99]

I have a new engine wiring harness that is wired to work with the dual resistor set up.  The connectors on the harness for the ballast resistor fit the "4-Pin" resistor.  The problem is that my Ignition ECU has only four of the five pins.  Wasn't the fifth pin in the connector for the second ballast resistor, and when the single ballast system came around they omitted the fifth pin on the ECU's?

The question is, will I be fine using the dual ballast resistor with the new harness built to use the dual resistors with the ECU's that I think were built to use the single resistor?

If not, can some one walk me through the modifications needed to convert my new engine harness to work with the single ballast resister so that everything works in harmony?

Also which field terminal on a dual field alternator is the positive one and which is negative?  I don't think it's marked on my alternator.  There is one field terminal that is lower closer to the power stud, and the other terminal is higher.  Judging from the length of the wires, I connected the green wire to the lower field terminal and the blue wire to the upper field terminal.  Is this correct?  Thanks for any help

[Nacho-RT74]

No prob. You can use double ballast resisior with 4 pins ECU. Just green traced red wire from ballast to ECU will arrive to nowhere on ECU. ECU feeds that ommited source internally from same blue traced yellow wire coming from spliced Blue line before the ballast, coming from ignition key.

4 pin ECU was introduced I think on lates 70s and was designed to make a plug and play job with 5 pins modules keeping same double ballast.

Brushes are the same you can feed positive blue wire or negative green wires to any brush for a while they are the right isolated brushes alternator kind ( squareback ) and isolators are in good conditions. I connected for example blue to the closer to stud because since the blue wire and black cross one over the other, then save from some accidentally short between wires. Yes is hard that happens but who knows.

[metallicareload99]

Thanks Nacho!  Got the car up and running, now it's time to start tuning