Another mystery wire

[shampooefficient]

Had the van running the other day. Ran very badly and I suspect the timing is out so that's on my list. However I discovered a random pair of wires.

Attached to the rear lighting loom. Two wires together. One grey/green wire and a brown earth running to the centre of one of the multi plugs joining the other earths there. I think it's probably related to lights or maybe a boot switch but any help would be appreciated!

(Earth/ ground, you know what I mean, it's a bad habit).

[Robsey]

I am sure grey/green and brown wires are for the rear number plate lights.

Grey/green is battery voltage to the two rear light units,
(Non-dimmed illumination)

And brown is the ground return for the lights

[silverbullet]

Its all in the Haynes Book of Lies and the current flow diagrams are lifted from VW own manuals, they cover all the essentials.