Hello all, my first post here, I did try searching but couldn’t find what I think I need.

So first the issue: I installed my own wiring loom for the trailer 5 years ago when I bought the car and all has been fine but recently when I have my trailer or bike rack hooked up, I have issues with the left sided clusters. With lights on, braking and indicating left, the side light dims and the indicator is weak.

My wiring tester tells me the trailer lights are fine but on the car, I have an issue with left side light and indicator. When the trailer is not connected though, the car cluster appears fine.

I suspect I have an earth issue and the question I have might sound simple but when is/are the earth(s). I have checked in the left side if the boot where the connectors are and all looks good, I have tried a new trailer loom but that didn’t help either. Switching the rear light clusters side to side and the fault remains on the left.

Any advise would gratefully received.
Rgds.

what year car is it?

On early models there is an earth ring terminal inside the car (behind the rear left light) for the towbar. White wire.

Sounds more like the trailer light board though

What indications is the dash giving you ?

The dash would come up with an amber symbol similar to a main mean, but is was in the lower portion of the speedo to the right of the needle, same height as the cruise symbol. This would appear when indicating under braking.

Sorry this isn’t more specific. I re-checked following your post and whilst the tester has been showing an error with the car, I bought cable and lights from Amazon and mocked up a new light board which worked first time. So, despite the tester, the issue was with the trailer. I’ve now stripped it all off and replaced and all worked today.

Excellent.

Sounds like rear fog light indicator

Are the trailer lights normal bulbs or LEDs?..

These are std lights not LED.

Having checked today, the dash light is indeed the rear fog. Interesting as the trailer did not have a fog light prior to me fitting one this weekend.

Glad I seem to have it sorted as we are due to tow quite a bit over the next few weeks.