Valeo Regulator Mod Puzzle

[belizesailor]

I recently acquired a new to me Valeo alternator to replace same which had failed on my Volvo MD2020. I pulled the internal regulator off and swapped in the one from my old alternator which was already modified for external regulation. Then, I noticed the extra wire on the original regulator....

This wire, long black with red heat shrink in pic, is soldered directly to the rear brush. This I assume is a mod for external regulation? If so, then how do you disable the internal regulator when its connected? Just disconnect the B+ lead (yellow wire)?

(My old regulator was modified by simply gutting the internal regular, soldering a lead to the distribution bars in the old housing and adding a couple of high temp resistors to derate slightly).