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Towing electrickery


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I know stuff all about towing electrics but I need to sort some lights for my boat trailer before the scuffers decide to chase me <_<

So I got a nifty set of magnetic trailer lights to clap on the back and take off before launching, because we all know what salt water does to things with electricity in don't we :rolleyes:

But the company I ordered the mag lights from didn't bother to send the extension lead I ordered at the same time so the plug is about 12 foot away from the socket on the back of my 90 :angry:

Where I'm confused is 12N and 12S ... if I understand correctly 12N (which is what my socket is supposed to be) is for lighting and 12S is something to do with caravan split charging systems.

A local store has a 6 metre extension lead which looks to have the same sort of 7 pin plug on one end and a matching socket on the other one - but when I went to buy it, its marked 12S. I assume it won't work as an extension for my trailer lighting?? Is the wiring & pin layout totally different for the 12S? The plugs look the same but I guess they aren't.

A simple question I know, but nobody here really bothers with trailer electrics, they just drive a bit slower and hope people can figure out what is going on :unsure:

Idiots guide required please :huh:

Thank you :)

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I know stuff all about towing electrics but I need to sort some lights for my boat trailer before the scuffers decide to chase me <SNIP>

Hi Stephen,

Does this help???


Sorry it's from a Volvo OC site but it's one of the best ones I could find after Googling.

Caravanning anorak mode to ON

You are correct 12S is the split charging and fridge powering side of things normally on caravans but also some trailer tents too. 12N is reserved for the road lighting side of things.

A 12S socket normally has a white or grey cover and a 12N normally black.

A 12S socket will not fit a 12N plug and vice versa.

Caravanning anorak mode to OFF

To extend the lead just make up a lead of the correct length with a 12N socket at one end wired as above and a 12N plug on the other . Alteratively you can I think buy coiled ones alreday made up.

The socket you will have seen in a store will be to allow a car to be parked fairly close to a caravan and to allow the internal lights etc etc to be powered from the vehicle battery. I had one of these in my early caravanning days but be aware they are not normally all wired up inside (Only the battery connections) and as I say the plugs will not fit anyway.

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Depending how nasty you want to be and what's available locally you can remove the plug from the end of your current setup and splice in an extension, either with trailer wire or whatever you can find. As long as you make a not of what went where, and just keep everything joined straight through, you will be OK.

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I likewise have an Anorak gland!

I also have a caravan although I don't know what it'll tow like when the +2" lift goes on the Disco :rolleyes:

Try Towsure what you need is part number E20 at £8.75 which is 6metres long.

I don't think it's worth trying to move the pins on a 12S as they are often barbed and damn near impossible to get out !

I'll keep taking the tablets, I promise!


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Simply, 12S will not fit 12N as the pins are in different places. Other than that, you may be able to pull out the pins and re-rig it to fit...


Ah ok I see - so the male pins and female pins on a 12S plug are arranged differently in the same plug body. I only looked at it briefly and thought "hmmm looks the same and surely an extension lead just passes all the wires straight through" but apparently not.

Oh well, back to the Bodgit & Scarper school of electrickery then :D

Thanks ;)

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12N = normal road lighting (socket & plug are normally black in colour)

12S = supplemetary for caravan use (i.e. fridge/interoir lights/battery charging.socket & plug either white or grey in colour,these will not fit a 12N socket/plug)

trailer 7 core cable for road lights -------------

yellow -- pin 1 nearside (left)indicator

blue -- pin 2 rear fog light (if towing vehicle is fitted with these then the trailer MUST BE fitted with 1 on offside or central on rear panel or a matched pair)

white -- pin 3 earth

green -- pin 4 offside (right) indicator

brown -- pin 5 offside (right) tail light & front marker light (if trailer needs them)

red -- pin 6 brake lights

Black -- pin 7 nearside (left) tail & front marker (if trailer needs them) & number plate light

hth :D

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sorry didn't resalise he was in the faulklands doesn't say that in his post sorry I spoke.

stick this in google earth it'll show you where BM is hiding

Third rock from the Antarctic - 51°40'S 57°51'W from his profile info under the armchair driving penguin
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