Thread: D4 Electric Trailer Brake Wiring

Originally Posted by clint

the blue led light on the Redarc stays in sleep mode, and doesn't allow me to change modes.

Clint, is the blue led light solid or flashing blue/green? If it's a solid blue light it means the unit is calibrated and should be ok. If all is ok, when you press the vehicle brakes the light will change colour to either purple or red depending on how hard you're braking. Does it change colour at all?

If it's slow flashing blue when you press the button, you're right, it's not recognizing a trailer is attached.

Perhaps try doing a complete calibration cycle as per the Redarc instruction manual. If that doesn't work, probably back to the installer.

Cheers,
Scott

It's a solid blue. Can't seem to change to user mode. Tried to reset the recalibration. That didn't work either. From what I can tell. The Redarc button can't do anything really ...that is access the programming functions.. Until it recognises that the trailer is attached.

Was worried as previously I had problems when connecting a trailer with electric brakes, as the brakes locked up, the guy said it was because I had a live wire in the trailer socket on the LRD4 on pin 5?

Thought by installing the Redarc this would not happen, as the pin 5 would be now variably control the signal from Redarc.

Would you know anything about multimeter testing ? Thought I might try testing the sockets.

I just installed one in mine over the weekend. I spent hours trying to work out how to do it and testing connections etc and finally found that the previous owner had already correctly wired it up and cut the pin 5 wire. All I had to do was connect to the correct wires that were taped up under the dash!


As you say, nothing will happen until a trailer is attached, except the solid blue light which fades out after a few seconds. I put a single LED test probe on mine and pin 5 was flashing the LED but not enough resistance to tell it there was something on the circuit. When I plugged it into a caravan all was fine.


If the sparky didn't do exactly what Sniegy said in this post it won't work. You must cut the wire behind the tail light after removing the tail light assembly. Cutting the brown wire inside the car behind the access door is no good, which may be what the sparky did.

Originally Posted by BigJon

Unfortunately using an "expert" can sometimes be the worst thing to do. Some of them refuse to listen to good advice / instruction, believing that their years of experience with old vehicles is all they need to know.

True, but my Defender isn't complicated, certainly not compared with a D4.

The way I interpreted Sniegy's posts is that the brown wire to pin 5 had to be cut behind the LHR light assembly in older models but the loom changed location and the wire can now be cut in the LHR storage compartment. I recall this as an update from Sniegy somewhere in the thread .... I had a search; eg 28Feb14 page 25 and 02Nov14 page 35. Having said that, the auto-elec who did my MY14 chose to do the cut (and red wire brake light splice) behind the LHR light assembly anyway.

Either way, the critical thing is that the wire is cut, otherwise the variable voltage signal to trailer via pin 5 is not happening as required. This could be the source of your issue.

But regarding the blue LED, as Bob said, normal operation without trailer is a blue light which fades out after a few seconds if you press the button. I think Redarc call this fade "breathing".

However, if you have a continuous solid blue LED with trailer connected and no fade out, that would suggest a different problem because solid blue continuous equates to calibrated and recognition of trailer attached. Alternatively, if you have solid blue continuous without trailer attached, that is not normal either.

You mentioned pin 2 blinking rapidly. No idea what that could be or how to test but perhaps indicates the flat-to-round adapter is faulty or just that pin 2 is not used by the trailer? I think pin 2 is for fog light?

Not sure if this is getting any closer to a resolution but at least confirmation of the cut wire for pin 5 connection should be a priority.

Regards,
Scott

When I got mine, it was showing I think the blue, constant light ... but it did not seem to be calibrated, and the calibration mode did not seem to initiate.

I had just attached the trailer, and nothing seemed to work.

I made a few phone calls, but had no luck with support as it was a Saturday afternoon ... so I drove the D4 down the road with the trailer attached, about 100 metres ... and suddenly everything was working. I think it calibrated itself at that time ... and from then on, no worries. It works alright ...

The Tow Pro can only be Calibrated with a trailer in tow.
Instructions tell clearly how to do this.

Cheers

G,Day All
wiring in my brake controller and things look a bit different in L/H cubby hole where splicing should happen. i checked sniegys posts and you mentioned there was a change to wiring in the thread for 2014 models. when you wired yours did the wires look like the attached pictures? i have no black wire being split to black and brown, only a brown wire with a black thing on it, this was under the insulation tape.
Andrew