D3 Electric Trailer brake wired-photo

**Meken** · 7th September 2014, 08:00 PM

Originally Posted by shining

I have probably mis-read your post, so apologies in advance but there are fuses in all critical systems in a D3/4/RRS. Suspension, transmission, lights, ECM, brake booster pump to name but a few.

Edited my posting - I meant to cut the wiring on the side after the fuse.
My P3 install details had the blue wire direct from controller to trailer socket.
If fuse blows how do you know? When the brakes don't work when needed! I take your point that there Are fuses in the systems in the car but I doubt any of these affect your ability to use the brakes when you put your foot on the brake pedal (and the car is so smart it will tell you there is a problem with one of those internal systems that are fuse protected )

**NTDisco3** · 30th October 2014, 02:03 PM

A quick question for anyone in the know, whilst planning to install a brake controller in the LHR panel as per Sniegy's instruction (thanks to all who have provided info on this - installing this w/e), I came across two plugs (see image) which do not seem to lead to anything and so was wondering what they were for? Diagnostics?

Can anyone point me in the right direction please?

**sniegy** · 30th October 2014, 06:54 PM

Originally Posted by garrycol

Ok thanks but that is not the case with my vehicle.

The rear fuse box has two seperate tail light wires going in and two going out - I have one of the fuses removed so it will not activate the trailer brakes when the headlights are on.

Cutting the power side of this fuse and supplying the signal from the brake controller will provide the brake signal through the old single tail light wiring to the blue trailer brake wire in the trailer wiring.

Sniegy - why did you run all four wires to the rear and not just the single wire that operates the brakes and connect the other wires (earth, battery power, brake signal ignition etc) from the dash.

Cheers

Garry

Hi Gary,
Sorry for the Late Late reply as i have been overseas & just catching up on some of the posts.
Reason i ran all 4 cables is thats what LR tell us to do. (Must follow there instructions) The only difference i would do on pre 10MY vehicles is run the +ve & -ve wires direct to the battery now.
The red & blue still need to be run to the rear & connected to the "Trailer Harness" & all connections be made to it & obviously modify the fuse holder as required.

Cheers

**sniegy** · 30th October 2014, 06:55 PM

Originally Posted by NTDisco3

A quick question for anyone in the know, whilst planning to install a brake controller in the LHR panel as per Sniegy's instruction (thanks to all who have provided info on this - installing this w/e), I came across two plugs (see image) which do not seem to lead to anything and so was wondering what they were for? Diagnostics?

Can anyone point me in the right direction please?

NT,
These are not the plugs you require. They are more behind the tail light & tucked up away a little.

Cheers

**NTDisco3** · 31st October 2014, 06:50 AM

Thanks Sniegy, although I was actually just wondering what the two plugs were for?

**NTDisco3** · 31st October 2014, 12:24 PM

Also, could you please let me know what size diode is appropraite for this application. I am installing a redarc tow pro with a nominal 18A current draw?

Thanks

**NTDisco3** · 31st October 2014, 02:25 PM

Hi Pete, did you mean the 5 pin on the 12N socket rather than the 12S socket please?

Regards,

NT

**sniegy** · 31st October 2014, 09:02 PM

NT,
I just use a 3amp diode. 80 cents from jaycar.
Also not sure what you mean about the 12n plug.

Cheers

**NTDisco3** · 2nd November 2014, 01:26 PM

Hi Sniegy, one last question (hopefully...) with respect to the power connection - black wire - which is connected to the thick purple wire from the trailer wiring plug. Does the black power wire get spliced into the purple or is the purple wire cut and the live end connected to the black wire and the free end of the cut purple wire simply taped up and left unused?

Regards,

NT

**Graeme** · 2nd November 2014, 07:17 PM

Originally Posted by Meken

If fuse blows how do you know? When the brakes don't work when needed!

I realise the comment was made a while ago but because the P3 displays the applied voltage on its trailer brake circuit when there is indeed a circuit, even when zero volts, then one would know if a fuse was blown because the display would not be the voltage display. This is the same as not hooking-up the trailer plug - no circuit, no voltage display.

However if an appropriate auto-resetting circuit breaker has been installed as per P3 installation recommendations near the power source then protection is already provided and makes such a fuse redundant and has the opportunity to reduce the availabilty of the trailer brake system.

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