Headlight and Sidelight Grounding (Earth) Wires

A new conundrum to vex us…
I’m tracing wires and color coding them with tape, using this diagram.

Notice in the lower of the two junction boxes, where the wires from the manette connect, there is a terminal with no wires on it.
My junction box had wires on all six terminals.
Notice also that each headlight, sidelight and pass light, has a ground (earth) drawn on the page.
My headlights and sidelights do not have ground wires.
But all the lights and horns work.
My junction box has four wires which I have not been able to identify.
I can’t find the other ends of them.

Am I right in thinking that the headlights and sidelights SHOULD have ground wires?
Maybe they have been cut off, and that these are the other ends of them?
Should they all go on that last unused terminal?
Did the creator of the wiring diagram simply forget or not bother to draw the grounds on that terminal in the junction box?

Hi Rob,

I’m away from home ( in your country ) but I think almost all earth returns are via the frame or body.

Here’s a more official wiring diagram.


Yes, from the '38 Instruction Book, thanks. I see it also shows that front junction box on the steering column with an empty terminal.
But my headlights have screw posts inside for ground wires. And my fog/pass lights have ground wires. I haven’t yet opened my sidelights to see what’s in there. One has a screw on the top of the fender pod painted over but the other doesn’t, don’t know what’s holding it in there.
Can’t guess what those 4 unconnected wires could be for if not grounds. Nothing is missing, everything in front works without them.

Well, I’ve figured out what those four extra wires in my front junction box are for. They are not grounds.
Dipping fog lights. The Bosch light on the left has a solenoid dipping function like the headlight, so it has an extra wire to do that. It works too! The Lucas light on the right also has an extra unconnected wire inside, so I suspect there was once a Bosch light there as well. The other two wires go to the dashboard and are not connected to anything. So there was probably a dipping switch for them on the dashboard at one time.
So what do we know about dipping fog lights? Were they popular somewhere, or required somewhere?

I think the idea of dipping foglamps is a contradiction in terms. Fog lamps work by having a low beam
The originals for your car would be Lucas FT 58.
The parlklamps did not have a screw to hold the lens in , That is the method on MK Vs. [ and SS100s . MGTC etc.
The SS and Mk IV had 2 copper spring clips coming forward from the bulb holder assembly and the jiggle in the end on these engaged with the ridge in the lens rim.
We have found that there are many repro lenses for the Lucas 1130 sidelamps and not always a lot of uniformity in sizing

The Bosch people must have thought it was a good idea. Maybe its not a fog light; it could be a long range driving light.
If so, then dipping would make sense.

BTW, what I thought was a painted over screw on the left sidelight turned out to be a red telltale. Only on the left side, not the right; I wonder why?