Thread: D4 Electric Trailer Brake Wiring

Hi Guys.

I’ve been following this for a while and thought I might share my experiences. I have recently purchased a 2005 L322 Range Rover and have a camper with LEDs. Unlike the D3/4 the Range Rover pulses brake lights and tail lights as well.

I’ve made my own “shunt box” to handle all 4 circuits (brake, tail, L & R indicator), to stop the flashing, disable the rear park sensors and allow the car to put limitations on suspension and what ever else it does (according to the manual quite a bit). I also wanted the trailer module (in car) to continue its function of monitoring the tail lights (I know LEDs rarely fail but they still can), the Rangie will detect if a LED light is functioning or not it just also causes them to continually flash as well…

Glad to report my box has achieved this, the car knows the trailer is there and does it thing, the lights don’t flash and if I unplug one of the tail lights (at the light) I still get the message on the dash that there is a problem.

Is there anyone in the Brisbane area (east side) with a D3/4 that is interested to test my little box on their car? My schematic is absurdly simple and I’m interested to see if it works on a D3/RRS or D4. If it works I’ll be happy to post details in the trailer section.

Also interested to know if the shunt available handles 4 circuits or just indicators and does it allow the car to detect a light failure?

Thanks Harlie. If I was near you I would offer my D4. I'm very interested to hear/see more on your solution.
I hope someone else can help out here with a local vehicle...

I have recently bought a D4 SE with the 3.0 litre engine and it is fabulous. Having read this thread while in the fact finding stage before deciding to buy the Disco I have bought an LED adaptor and a Prodigy P3 brake controller for pulling our Bushtracker caravan. I had the P3 fitted by a 4WD specialist but am having some problems. When I have tried to set up the power level on the P3 by applying the manual knob there is no response from the caravan brakes. I pushed the power level to the maximum of 12.8 but still got no obvious response from the brakes. When I applied the foot brakes the voltage went to a maximum of 3.4 volts which the auto electrician advised, when I took the Disco and caravan to be checked, is insufficient to operate the brakes on the caravan. They couldn't find any problems with the wiring and so it is possible that the P3 is faulty.

I'm wondering whether anyone else has had similar problems?

Andrew

Andrew,

I fitted a P3 to my D4 (also fitted one to my D3) following Sniegy's instructions and it works fine. Perhaps before you pull the unit out, use the boost button (top right button IIRC) and try it set to a different level (you can choose between 1 and 3) and see if that helps.

Cheers

Thanks Cameron

I set the Boost setting to B3 and with the power set at maximum I found that when I applied the manual level the D4 and caravan were stopped from about 20kph. This was only a gradual slow and stop and no hint of really effective braking. From the instructions that came with the P3 I would have expected the brakes on the caravan to lock up at these maximum settings. The controller is obviously working to some degree but it worries me that there doesn't seem to be enough braking from the van.

Any other thoughts? I might just go to a brake specialist and see if they can help.

Cheers, Andy

Andy,

That's a bit of a bugger. I run my 21' van on 6.5v with no boost.

The only other thing I can suggest is the problem may be with either the LED module or the van itself. Is the LED module tapped into the existing van wiring or do or the wires run through the module? Perhaps check all are connected properly. Have you tried another van or trailer to see if that works. That might help pin point the problem.

After that I am out of ideas other than having someone check the P3 unit. At least it can be Removed without the wiring harness.

Best of luck.

Hi Andrew,

I have a D4 3.0 and Prodigy P3 connect to a Bushtracker as well. Install the P3 myself following details on here, works fine, though for first few 100K had accidently turned the power right down an did not have much breaking on van, did not really notice as I was taking pretty easy at first.

I have just hooked up and taken a few measurements for you, closest thing I can do to going away for now. The P3 has some really handy diagnosics you may not have come across yet. Access the by pressing the bottom right hand button (looks like and open book) and then arrow down to help, select that with OK (the book button), arrow down again to troubleshooting and select that with OK (the book button).
You can now arrow through 4 readings which should help diagnose the problem. ie.
1. Battery Voltage
2. stop light voltage (what you get to trigger the thing from the brake light)
3. Output voltage
4. Output Current (this should be very useful)

Here are my results. First hook up, have the motor running, (well power on at least). Set power to maximum for the testing. (however I only need about 6.0 or less in normal running.) Set to B1 for now.

Check for these results.
Measurement -- Battery Voltage
-------------------------------
No brakes applied --> 13.84 Volts ie battery voltage
Manual Override applied --> 13.77 Volts. (A slight drop due to current being draw, if no drop you have big wires or not drawing any current which we will pickup further down)
Press foot brake --> same as Manual Override

Measurement -- Stop Light.
---------------------------
No Brakes --> close to 0
Foot Brake --> 13.84 ie the full battery voltage
Manual Override Applied --> 13.39 (This is output from the P3 and is what goes back down the brake light wire to put brake lights on when using Manual Override)

Measurement -- Output Voltage
-------------------------------
This is what P3 thinks is going to the van.

No brakes --> close to 0

Foot Brake --> 1.5V (B1 (Boost1)), 3.4V(B2) , 3.4V(B3). The pridogy is proportional, if you are not actually stopping (ie decelerating )it wont put the full voltage out as it knows you are not hard on the brakes, this is why it is smooth when you apply the brakes, B2 and B3 seem to put out the same but more than B1 for this test.

Manual Override Applied --> 13.39 Volts


Measurement -- Output Current
-------------------------------
This should be the really good one, this will be the actual current going to the magnets on the van, or somewhere else if not there. So if we have 4 wheels on the van, 4 magnets in parallel, they are around 4ohms each I read somewhere, so we should have about a 4/4 ie 1 ohm load, at 12volts, we are looking for around 12 amps. ( I=E/R Current=voltage/resistance).

Here is what I got.

No Brakes --> 0 is good
Foot Brake --> 1.1amps (B1), 2.5amps (B2 and B3)
Manual Override Applied --> 11 amps

So the 11.0 amps is operating your magnets or going somewhere else.
On a power setting of 6.0 around 5.9amps in lieu of the 11.0 amps.




Also check you have brake type set to electric and not hydraulic over electric. I don't think it alters the results here but probably effects the way it applies the power to the brakes.

Interested to see what you find when you measure, no tools required, just push the buttons on the P3 in the right order.



regards
Gerry

I will be taking delivery of a D4 soon and I have been reading the posts on electric brake controllers and LED shunt modules with interest.

Thanks for all the info on brake controllers. It will make life much easier when the time comes (as my camping trailer has elec brakes)

Regarding the LED shunt module... isn't the module simply providing resistance on the necessary circuits? Therefore, wouldn't a product like the following from Narva do the trick of curing any D3/D4 induced LED pulsing, as well as letting D4's know a trailer is attached?
LED Load Resistor - Products - Narva

I also found a different brand at my local ISP trailer parts shop.

Would these load resistors cure the problems? They are relatively cheap ($40 pair at ISP) and would be easy to connect up

Any advice gratefully received
Pawky