7 pin trailer plug output

Gear_box

Hi could someone please tell me what the 8th wire that is connect to the blue fog light wise do?
Is it a switch wire to turn off the car rear fog light?

thadg

have you a pic?

most sockets that are wired (car side) are not wired back to the fog light anyway, are you talking about the trailer side or car side that you have the spare wire?

you could hook up the trailer fog light if its an ifor Williams trailer with the brake lights if the car socket isn't wired for the fog light outlet, at least you would always have brake lights working then, if 1 blew

Gear_box

Have a picture but won't let me post.

Gear_box

There is an 8wire connect to the blue fog pin via a bi-metal switch off some sort in the 7 pin socket

Gear_box

What I am trying to do is change the 7 pin to a 13 pin the car has a trailer harness

Gear_box

But the tow bar was fitted with a 7 pin

thadg

you can buy an adapter.

or else this is the 13 pin
http://www.uk-trailer-parts.co.uk/wiring-a-13-pin-euro-plug/


this the 7 pin
https://www.pinterest.com/pin/380976449703550166/

Gear_box

Melodeon

Here's the picture:

thadg

the idea of the black wire is to switch off the fog light in the car if you turn it on when you tow the trailer to avoid a red glare.