Thread: D4 Electric Trailer Brake Wiring

Originally Posted by Jimlr

Think I'm sold on putting a tow pro in the new 14my d4, which is now only a couple of weeks away. Only generally towing a light load, just over 800kg, occasionally a van.... Is the tow pro going to be a good choice?

Is there anyone in sydney worth trusting with the install, and drilling a 10mm hole in the dash!???

I assume the dealer will just farm it out to the local auto sparky if I ask them to do it ... then I can't necessarily insist a diode goes in, exact placement etc....

If you're ever in Melb, happy to do it for you.

Cheers

I just had a Redarc Tow Pro installed to replace the knee bashing P3. The rotary dial fits neatly behind the hand brake control.

Not a fan of fitting it on the lower console (around handbrake area on the flat surface) because of its vicinity to being lent on, stood on, liquid dropped on, phone, purse, wallet or for that matter anything dropped on etc etc.
I still fit in either the light switch binnacle (R/H/S) or the steering column cowl on either side depending on 1. customer request 2. Electric steering column switch then determines.

Cheers

Originally Posted by mowog

I just had a Redarc Tow Pro installed to replace the knee bashing P3. The rotary dial fits neatly behind the hand brake control.

Hi Mowog, who did you have the Tow Pro installed by? And have you tried it out yet? I am lining up the P3 or Tow Pro but unsure about Redarc due to this being the first of their models with an accelerometer in it.

Originally Posted by Jimlr

Think I'm sold on putting a tow pro in the new 14my d4, which is now only a couple of weeks away. Only generally towing a light load, just over 800kg, occasionally a van.... Is the tow pro going to be a good choice?

Is there anyone in sydney worth trusting with the install, and drilling a 10mm hole in the dash!???

I assume the dealer will just farm it out to the local auto sparky if I ask them to do it ... then I can't necessarily insist a diode goes in, exact placement etc....

Talk to Frank at ATV Automotive in Five Dock 9712 8001 they are a LR specialist and apart from doing all aspects of maintenance and repairs they also do in house installs of electric brakes, dual battery kits and fitment of all aftermarket accessory's and from what I have seen over the years of going there they do a very tidy job at a reasonable price.

Thank you sniegy (and others) for your efforts and sharing your experience. My question relates to tapping into the bake light line (red) and the need for the diode.

It is clear why you need the diode if you tap into the red wire. What I would like to find out is if anybody has tried to tap into the brake pedal switch (cold end of the +12V, the pin that becomes +12V when the pedal is depressed). This is the way Land Rover connects the controller in the USA version of the car and in the latest AUS models too.

The pedal switch has four pins forming two pairs of contacts: one contact connects to +12V and the other to GND when the pedal is depressed. Tapping in there would avoid the need to run long cables and the use of the diode. Are there any traps? Has anybody tried this? Thanks.

Note: Do NOT depress the brake pedal if you remove the switch or you will break it...

Hi ken - what you have asked is the way the Brisbane LR dealer auto sparky insisted on doing my installation. However instead of tapping direct onto the wire he installed a 4 pin protected relay which used a constant 12 v feed - brake light cold wire drove the coil and output was connected to the downstream cut of the brake light circuit. Red P3 wire was also connected to output. So if you use brake pedal - 12v pulls relay coil which then feeds the constant 12v to the brake light circuit & the P3 red wire. If you use manual on P3 then the P3 sends 12v down red wire which illuminates brake light circuit.
The relay prevents any possibility of current back feed into the brake light switch & into the other circuitry / trailer ecu etc. this is a 2008 model so who knows what has changed in the electrics. ?
As far as my opinion goes it is essential to use an auto sparky who has experience with LR. The 1st bloke I had did a pretty poor job with no idea on the electrics of the car. When I took it to the dealer to troubleshoot an issue, they wouldn't let it leave until they had redone all of the original blokes wiring etc they were so concerned about it.

Originally Posted by ken224

It is clear why you need the diode if you tap into the red wire. What I would like to find out is if anybody has tried to tap into the brake pedal switch (cold end of the +12V, the pin that becomes +12V when the pedal is depressed). This is the way Land Rover connects the controller in the USA version of the car and in the latest AUS models too.

Firstly its not clear to me that the diode is required, indeed I didn't fit one initially and can see no reason to do so.

I suspect that connecting as you suggest will be OK simply because the US version of the same year model connects to the same spot. Electrically the signal wire will be weakly tied to ground so that it doesn't float when no input from the switch and the bcu processor should have a high impedence connection to this input with any residual voltage above 5V removed, making the bcu immune to electrical damage from low voltage inputs. Programming-wise I would not expect the US version to apply different logic regarding any conflict with the normally-closed contacts of the switch.