Valeo Alternator Regulator Wiring

[Aeroade]

Purchased a new Valeo alternator to replace the same type on a Volvo Penta 2003. On accessing the regulator to change it to the same external regulation as the old one, I found an additional Brown wire coming from the regulator and disappearing into the alternator body. Anybody know what it does?

[Ding Duck]

Does this help?
http://springnuts.org/docs/alternator.pdf

[Aeroade]

Traced it to the diode pack and is common with D+ and joins the yellow voltage regulator +ve to the brushes. Alternator is working but regulator is max field voltage. More work to do.