Thread: Problem with trailer plug electrics

If you are getting some lights on the trailer working but not others then it's either the lights themselves (all of them faulty at once is very unlikely) or the wiring. Check every pin on the car trailer plugs to see if they work as they should with a multimeter. If not, then you've isolated the problem to the car harness setup. If it's ok then move onto the trailer wiring and do the same proceedure. My money is on a loose wire or corroded pins in the car plug.

Originally Posted by rocket rod

If you are getting some lights on the trailer working but not others then it's either the lights themselves (all of them faulty at once is very unlikely) or the wiring. Check every pin on the car trailer plugs to see if they work as they should with a multimeter. If not, then you've isolated the problem to the car harness setup. If it's ok then move onto the trailer wiring and do the same proceedure. My money is on a loose wire or corroded pins in the car plug.

Thanks for the thoughts but no loose wires, no corroded pins - all checked very thoroughly by an auto electrician on Saturday. Unfortunately he had limited time to look further AND it was ****ing down with rain. He also checked both sides of every fuse in the car and had a good look at the way the loom was wired.
I’m going to look for broken wires through the week.
I’ll report back with what I find.

Prioritise getting the car to see the trailer, ie the trailer icon to illuminate with the blinkers.

We are lookiing at 2 seperate issues here.

Vehicle not recognising trailer is plugged in is a LED light issue. It wont be causing the other issues.


The second problem is the one to focus on - no tail or brakes...

Start by getting a multimeter and probing the trailer plug.

Well, have solved the problem. Whoever originally wired the car completely messed up matching the wire colours. Swapping a few around has resolved the issue.
thanks for all the advice. It was just a process of doing things one by one.

Originally Posted by Odysseyman

Thanks for the thoughts but no loose wires, no corroded pins - all checked very thoroughly by an auto electrician on Saturday. Unfortunately he had limited time to look further AND it was ****ing down with rain. He also checked both sides of every fuse in the car and had a good look at the way the loom was wired.
I’m going to look for broken wires through the week.
I’ll report back with what I find.

Originally Posted by Odysseyman

Well, have solved the problem. Whoever originally wired the car completely messed up matching the wire colours. Swapping a few around has resolved the issue.
thanks for all the advice. It was just a process of doing things one by one.

Presumably not checked that thoroughly by the auto electrician 🥺

Glad you've got it sorted.