Strange intermittent fault on 13 pin socket

[mainline]

my caravan isn’t lighting up tail lights, but all other lights work fine.

However… while testing, I got a strange sequence of events.

I’ll also point out that the 13 pin socket has the left and right tail lights on different pins, so whatever it is, is affecting both sides.

The 13 pin is exactly the same wiring as the 7 pin.

Left and right tail lights are separate, one side also supplies the number plate light.

The 13 pin sockets have extra pins for reversing lights + supply etc.

 

[littlespark]

I found it a little weird that replacing only some of the lights on one side then allowed the other side -where I hadn’t changed anything- to work.

If my thoughts are correct, and it’s some sort of overload protection in the vehicle relay, it must be on the shared earth that serves both circuits of side lights.

Or maybe not. Thinking.

That same earth serves ALL the road lights… and they all worked. Just the side lights were off.