Hi Morganic
I'm no techie but I had a problem when having 13 pin wiring fitted to my new Kia Sorrento earlier this year. I wanted to get the wiring 100% correct as I was, also, having ATC fitted to my 'van AND I, also, wanted the Kia specific kit which would plug into the car wiring and turn of the reversing sensors when the 'van was hooked up. Contrary to my instructions a local towbar specialist (????) fitted twin N and S sockets and scotchlocked it into the car's wiring.
I gave up the above "expert" and ordered a Sorento specific wiring kit AND supplementary kit for fridge, etc from Towequipe for my usual mechanic to fit. Even though I had paid extra for the supplementary wiring kit when the mechanic had got the car all stripped down he found that there was still a pin missing from the 13 pin socket. Towequipe had to send out another pin and wire!!! The kit that Towequipe supplied was made by Westfalia, ie, German. The electrics are now all correct but what a faff about.
There seems to be an AWFUL LOT OF CONFUSION about fitting 13 pin electrics. There are different wiring colour diagrams and some UK dealers are providing 13 pin cable with wire cores of the wrong thickness I have a feeling that Western towing may have been previously mentioned as supplying 13 wiring cable with the correct sizes of wiring, ie, thicker core for the fridge connection.
I hope this helps.
Tim