Grateful for anyone's help as I'm not getting 12 V at my 13-pin socket for either of the tail lights. Indicators, brakes and fog lights all work fine. I have taken the back off the socket and checked the actual wires to ensure it wasn't a loose connection into the rear of the socket and still no 12V so definitely nothing coming down the wire, so to speak. This is with car started and car lights on.

The car is a 2011MY 4.4 TDV8
The tow electrics are a genuine Westfalia plug and play kit. I fitted it myself but I can't see how I got it wrong as you literally just plug the kit into the socket in the spare wheel well and almost impossible to mess up.
I did not need to edit the car's CCF file with my IID Tool but I have checked and the CCF and you can see the settings below

Click image to enlarge

Have a read here.

https://www.fullfatrr.com/forum/topic60154.html

If you have a multimeter you could test the car plug that your wire is plugged into to see if there is 12 v on the car side.
The next thing to do would be a continuity check on the new loom from the car end to the 13 pin socket this would identify if there was an internal wiring issue - again you need a multimeter. 2012 tdv8 Westminster arrived Jan 19 gone Dec 23

200 TDi discovery bobtail gone
RR classic v8 bobtail gone
300 tdi Discovery 3 dr gone

Just use a multimeter on the socket, turn on the side lights and check you've got 12V.

Also, just to check you haven't got LED trailer lights? 2015 Range Rover Autobiography 4.4 SDV8

Ajmngn wrote:

I haven't checked fuses but surely there's not a separate fuse specifically for the trailer sidelights in the fusebox, or is there?

So, turns out it was the fuse, great news but frustrating as I’d been trying to trouble shoot it with the multimeter! Haha, just my luck! The passenger compartment fuse box has three fuses relating to the trailer electrics:
- one 30A which is for the trailer circuit (I assume some kind of master fuse)
- one 10A for the trailer reverse lights
- and one 10A for the trailer side lights.

After checking for continuity with my multimeter it was clear the fuse was blown and once changed we’re back to normal again. Phew! I like it when it’s an easy fix!

Lesson learned: always check all available fuses before delving deeper into any electrical problems!

Thanks for the suggestions all as it certainly helped me troubleshoot in a much more focussed way! Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!