Unknown wire to my Voltage Regulator RB106/2

[CG901]

I have a black wire, not appearing on my S1/2 wiring diagram going from the #3 pole of the fuse box but not yet connected to my regulator. Any idea which terminal it connects to?
Car was converted to negative ground.

[robertverhey]

Hi these pics I took when dismantling may assist you. My wiring appears original. Ignore the yellow wire, that's for an electric fuel pump fitted by PO. And note the "semi-fried" nature of my earth lead from regulator to solenoid. Caused, I think, by the engine to chassis earth lead being broken, so the starter motor (or maybe the alternator?) was finding an earth via this relatively puny lead.

The wire you're asking about just seems to be a power feed for the fuse box lower fuse, which, as you'll see, is a "piggy back" extension from the upper fuse in my case. Hard to tell where the piggy back lead from upper fuse goes to in your pic, but you could just reconnect it to the lower fuse spade and dispense with the black lead.

Sorry the pics have inverted themselves in the uploading process, they will make more sense if you find a way to rotate them

[CG901]

Robert, thanks for this. Your photos are consistent with the S1/2 wiring diagram in the WSM. So it appears my black wire coming off pole #3 of the fuse box would power up the horns directly as it was originally somewhere on the VR. Otherwise, the ignition switch would have to be "on" to power the horns. Confused as to why there is no bridge as your photo correctly shows from pole #1 to pole #3. I suppose that I would use the black wire to complete this and that would allow power to flow to the horns when the ignition is on?

[robertverhey]

Hi, looks Like the "bridge" wire on your fuse box goes to another spade on the same plane, ie it's not really doing anything as these spades are all common to each other. So taking your bridge wire to the other plane would return your wiring to standard, same as mine. In doing so the black wire would become superfluous

Have I got that right?

[CG901]

Yes, I agree, however, I would use the black wire for the bridge as the original white bridge wire is not present.
Will accomplish same goal.

[RogerFrench]

Black wires are earth, (or ground on the left side of the Atlantic), as standard. This is a Prior Owner wire, and should be treated with great care. Earth wires on the fuses may lead to loss of sanity.
If you need a bridge, make a new one with white wire.

[CG901]

OK, good advice. Will do. Thank you for all your valuable advice!