The B20 I rebuilt some years ago has been running with the stock 30 amp generator and regulator. Since the B20 block also has the threaded boss for the alternator, I've been looking to install one.

I had a new external voltage regulator (1308 030), Bosch # 192062005 and sourced a used but working 55 amp alternator and tensioning brace, as well as the correct 3 terminal plug from regulator to alt.

Here's my question.

In the harness to the regulator, on this body, there are 3 wires only two of which were being used:

heavy gauge black - this connected to reg and now will go directly to alt.

light gauge red - from wiring diagram, this goes back to the "generator light" in the dash

light gauge black wire with female spade connector that was unused and left tucked back in the sheath

What would this lighter gauge black wire have been used for, or where does the other end emerge and to what is it connected?


thanks