Thread: Electric Trailer Brakes

I drove down to Warrnambool on Sunday to pick up my camper.

As predicted the electrics were interesting. Connected everything up - all lights worked as they should, brakes were off.

I went to drive away and the trailer brakes were on. So I disconnected the plug from the car and went to a try area to try and work out what was going on.

I tried disconnecting various wires in the plug without any success. The brakes would only release when the plug was disconnected from the car but would not come back on until the brakes were applied - logical conclusion was the brake light wire was also wired directly to the brakes - problem was that when the car brakes were released the trailer brakes did not.

So not having time to stuff around and as the camper only weighs 600kg I cut the wires to each brake on the trailer axle.

Now this is where is starts to get weird - the brakes did not release and when the trailer plug was released from the car they brakes released. Something weird going on here. But with the plug reconnected to the van lights worked the van brakes came back on even though the wires to the brakes were cut

I then went to super cheap and bought a trailer board with lights and cable - not totally compatible with the RRS systems - blinkers work by themselves, the tail lights work by themselves and the stop lights work by them selves but if any two are on only the tail lights work - also using the blinkers cancelled cruise control in the car .

When I got the trailer home - the light board worked OK on my 101 and my box trailer worked on the car - the RRS just did not like the light board.

So some weird wiring things going here. When the weather improves I will pull off the drums and check the brakes out and rewire back.

Garry

Originally Posted by garrycol

I then went to super cheap and bought a trailer board with lights and cable - not totally compatible with the RRS systems - blinkers work by themselves, the tail lights work by themselves and the stop lights work by them selves but if any two are on only the tail lights work

Caused by no earth to the light clusters so they get their earth through other lights not powered which in turn obtain an earth via the car's light cluster earth.

edit: This could be the reason for all the wierd behavoiur - no earth to your vehicle socket.

Originally Posted by Graeme

Caused by no earth to the light clusters so they get their earth through other lights not powered which in turn obtain an earth via the car's light cluster earth.

edit: This could be the reason for all the wierd behavoiur - no earth to your vehicle socket.

I agree so what I need to know is it the board that doesn't have a return earth (not likely as it is designed to work this off the trailer - and it does work on my 101) or is it the way Landrover have set up the wiring in the back of the RRS - more likely this (most likely another landrover brain wave).

Once the weather improves I will be double checking the earth in the black socket.

Cheers

Garry

Originally Posted by Graeme

I assume the RRS uses the same wiring as the D3 & D4 whereby the pin that is used for trailer brakes has a 2nd tail-light supply, so when the lights are on, so are the brakes! To make a temporary fix, remove the wire from pin 5 of the trailer plug (its probably blue).

Yep mine is as you describe. So the trailer brakes would have a full 12v when the lights were on (doesn't explain why the brakes were on when the wires were cut - but one thing at a time). If I cut the relevant tail light wire in the RRS trailer wiring loom will that cause any problems in the car?? I will connect the brake controller wire to this wire on the plug later when I install the brake controller.

Thanks

Garry

Cutting that wire will have no effect on the vehicle.

Garry, we cut the wire at the fuse block in the cargo area, this also gives you a connection point for the trailer brake feed wire.
You would of probably noticed that the rear of the trailer plug is solid & filled with silicon so no dirt or water can corrode the connections in the plug.

Lift the lid on the floor cargo area where your tools are & there should be a fuse block located on the lhs, unclip the fuse block & locate the side where the brown & black wire are next to each other, now cut the brown wire 2 inches or so away from the fuse block & solder the brown wire from the fuse block end to the black wire next to it, this will now make 1 park light circuit.
Now the blue wire from the trailer brake unit can connect to the brown wire that runs into the loom.
HTH
Cheers

Thanks for that didn't even thing of doing it at the fuse block.

Cheers

Garry

I discovered why the brakes weren't on all the way home when I bought my pop-top - its aux supply is from pin 5. However if I'd turned the fog lights on it would have been a different story, with the brakes wired to pin 2! My guess is that trailer plug wiring has standardised in the last 20 years and mine was different.