Thread: Quick answer needed for blue wire trailer brakes

Whatever Scouse says.

The need to cut and join wires arises from the differences in European and Australian use of the trailer socket/plug pins. Europe has a separate wire/pin for the left and right trailer tail light. In Australia one of those pins is allocated to trailer brakes.

Without the modification to cut power to the trailer brake pin, the trailer brakes activate when the vehicle tail lights are turned on. The modification involves combining the left and right trailer tail light circuit into a single circuit going to the appropriate trailer pin.

The brake controller will send power to the trailer circuit that has been cut.

So, you are saying that if I join the wires from pin 5 and pin 7, then connect the brake wire to this?



The only issue is that the wires on my photo above (top of page) start with pin 1 (red) pin 2 (blank) etc, dont line up with the chart....?

Thanks
Tristan

Ok, I think I have got it, As with the above post and image the diagram refers to the pins on the trailer socket. The wires coming out off the plug (1st post image) doesn't matter with the pin alignments, it's the colours that matter.

So cut and join the blue & brown and run the blue brake lead to that.

Is this correct?

Thanks for your help.

On your chart it is the black and brown that must be joined on the trailer side of the plug you have shown and the blue brake wire then connects to the brown wire going to the trailer plug (ISO 1724).


Check the circuits carefully with a multimeter because if your car is not owned from new a previous owner may have already done the mod. On my D4 it took me ages to figure out that the previous owner must have had a brake unit fitted as the wiring was not what I expected when checking with a multimeter. The wires were actually connected near the tail light outside the car where it could not be seen easily. I was expecting that it would have been done in the side panel where there was easy access to the wires.


Once I figure this out it was easy as the appropriate wires were already in place from the dash area for me to connect the brake unit to.

I don't have access to my RR so I can't check. However, I agree with Bob, from your chart the black wire remains fairly intact. The brown wire is cut near the driver side between the fuse panel and the trailer plug. The fuse panel end of the brown wire is spliced into the black wire, so the L & R tail light trailer circuits merge into one. The trailer plug end of the brown wire connects to the brake controller. Your brake controller should also connect to power and to the stop light circuit.

My reply above is referring to the standard round black LR trailer plug (socket). Is the pic in your initial post of a rectangular trailer socket connected to the RR, or intended for connection? If already connected, there has already been some modification which may or may not include merging the trailer tail light circuits.

Wow, now I'm confused..I thought that all the plugs etc were AS here in OZ, How do I tell that I have a ISO version?
Yes I think I have the standard LR trailer plug, although my RR looks like it has never towed anything ever. So I doubt any other mods have taken place?
Oh and the original pic, that's the black connector that goes into the white box next to the fuses etc. (sorry 1 or 2 glasses of wine this late fumbles the grey matter cells!)