On Mon, 23 Apr 2018 10:02:33 +0100, Chris Green wrote:

W - I still don't know what this is.

Probably tachometer....

https://www.lima-shop.de/forum/board7-lichtmaschine-allgemein/19-klemmen-anschl%C3%BCsse-bezeichnung-der-lichtmaschine-generator-und-am-regler-f%C3%BCr-bosch-valeo-hitachi-magneti-marelli-motorola-etc/
http://www.dsclub.de/forum/read.php?1,37759

The W doesn't seem to stand for anything, "Drehzahlsignal" meaning rotation
count signal is completely W-free. But then a couple of manufactureers use "61"
for the "L"-amp connection...

Thomas Prufer