MY13 Discovery 4 Electric Trailer Brake Wiring

[DiscoDavey]

OK you are probably thinking "not another ETB question" and you'd be right.. BUT I have followed the excellent instructions on this forum and have run into a little trouble.

Unless I have completely missed something obvious (very possible) then it appears that MY13 wiring is slightly different - only in that the splice joint where the brown wire splits into black and brown is now INSIDE the car cabin where the tow hitch lives. I took off the tail light assembly and followed the black & brown wire all the way back to this point.

As you can see below I have wired it as per sneigy's instructions (except for location of the splice) and my black wire connects to the blue wire at the Brake Controller and the red wire runs connects to the red wire at the BC.

The problem
The Electric/Hydraulic brakes do not work! When the manual over ride button is pressed the trailer bake light come on. When the car brakes are applied, the same brake lights come on! It is like a wire is crossed but I can't work it out.

If anyone can help I would really appreciate it. I am at a loss!

I have a P3 EBC fitted..

56586

56587

http://www.aulro.com/afvb/attachment.php?attachmentid=56588&stc=1&d=1360481938

[Graeme]

When the manual over ride button is pressed the trailer bake light come on. When the car brakes are applied, the same brake lights come on!What are you expecting? This seems correct although it doesn't explain why the trailer brakes don't work.

[disco4now]

The P3 has a diagnostic mode that can be quite helpful. See link below for what you get when its working. It allows read out of current and voltage just by pressing a few buttons on the P3. The lights you are getting seem OK to me.


http://www.aulro.com/afvb/d3-d4-rrs/97935-d4-electric-trailer-brakes-post1419157.html#post1419157

Regards
Gerry

[DiscoDavey]

What are you expecting? This seems correct although it doesn't explain why the trailer brakes don't work.

When the trailer over-ride switch is activated on the Electric Brake Control, the brakes should activate and I would have thought the brake light on the trailer would not? However, maybe the EBC also sends a stop light signal to the trailer regardless if a foot is on the brake when over-ride activated- that would be why there is a stop light cable running to the brake pin! Would make sense.

Putting a voltage meter on the pin shows only brake light pin working.

I ran the diagnostics and it all looks OK although I am not sure what output readings I should be getting.

I'm going to assume I have a bad connection on the blue cable. I'll re-connect and report back.

[sniegy]

If you are just checking the pins at the rear of the Disco, then the readings will not be correct.
You need to have as we do a dummy board with loads & you then get correct readings.
(Have been caught before)
It all looks correct.
If you apply the manual lever then yes you will get a brakes to operate at the trailer, you don't use the EBC unless the trailer is connected.

Cheers

[bushshak]

Hi All,
I am new to this forum and have now had my MY13 D4 for just over a month and have been following all threads on trailer wiring with interest. I am a convert from Toyota (4 x Prados) and I have found the descriptions and hints very helpful. I finally got to wire my P3 brake controller in over the easter break and all worked fine initially.
It seem now though that the trailer brake lights do not operate nor the brake controller as there is 0 volts on the 'red' feed wire from the front.
I have wired the controller red wire to the trailer red wire with a diode connecting to the red feed wire. This is so that when the manual overide lever is activated on the controller - the brake lights on the trailer (van) will operate but not feed back to the vehicle.
I have read that others have had similar issues which appear to fix themselves. Can anyone please advise where I should go next or possible causes as at this point I have no trailer brake lights? I have been unable to find any fuses that may possibly be the cause.
Cheers
Keith

[sniegy]

Is the diode in the correct way?

The Kathode end needs to face the brake controller not the rear of the vehicle.
Did you connect the red wire from the ETB unit to the red wire at the rear of the vehicle?
(Also be careful a there are 2 wires, it is the smaller one)

Let us know.

Cheers

Sent from my iPad using Forum Runner

[bushshak]

Thanks Pete for the quick reply.
Yes the diode is correct - I have 0volts at the anode when brake applied so issue is nothing from the front of vehicle.
Manual overide works fine.
As I said it worked fine to start and I have LED lights and shunt resistors installed on indicators. All other lights work ok and trailer seen as reversing sensors disabled etc.
Cheers
Keith

[bushshak]

Hi Pete,
I have attached a photo of the connections and as can be seen from clear heatshrink the diode is correct.

[sniegy]

I can see the mistake, albeit a simple one to make.

The diode is in line with the brake circuit(factory wiring), you are basically stopping the signal to the rear lights.

The diode needs to be inline with the wire you ran.

I hope this makes sense.

[bushshak]

Hi Pete,
Unfortunately it is not that simple.
The circuit as I have it will work correctly. The difference is that the diode will block or prevent any feed back from the P3 to the rest of the system but sill operate anything upstream of the diode including the brake lights on the trailer or brake controller. This setup will operate the trailer brake lights when the manual switch on P3 is operated but does not prevent the lights from working via the in feed (factory wiring).
The issue I have is that I am not getting any voltage on the anode of the diode (factory wiring) thus not operaterating anything beyond.
Cheers
Keith

[sniegy]

Hi Keith,
Having another look at the diode which is correct, i took the cable running the wrong way around.
What you have done is correct.

All i can suggest is checking fuses & making sure the connection to the red brake wire is secure.
Fuse 14 behind the lower glovebox from memory, (mine anyway 10MY)
also be sure that you check them all (trailer fuses) as there are seperate circuits for just the trailer, your HB will detail all the fuses.

HTH Cheers.

[bcl]

Have you checked the voltage before the connector on the fuse side/ factory side of the connection. Could be a bad join.

[Dingo Charlie]

Hi,
Do you have constant power hooked up to pin 2 the reverse pin? With hydraulic/electric brakes generally your unit on the trailer has an led light on it, this will light up when you do the above and you are then good to go.
What sort of brake system do you have on the trailer?

[bushshak]

It would appear that I have been outsmarted by a car!
It seems that the computer in the D4 shuts down several light circuits after a time whenever the driver's door is left open - brake lights being one of them.
I am yet to figure out what combination of open doors etc shuts down what but suffice to say I have learnt about the trailer brakes.
So at the end of the weekend of checking and double checking I had, purely by chance, my lights back and all working as they should without any physical changes.
Cheers and thanks to all for your input.:)

[DirtDigger]

I am not sure about the diode installation. Does the P3 red brake sense wire supply current that would activate the car's brake light circuits if a diode was not installed? Having just posted tonight about issues I had with an auto sparkie installation stuff up titled "auto sparky woes and errors" my fix did not include a diode in the brake sense red wire and I have not come across any issues as yet with my installation of the Prodigy P3 into the D4's trailer wiring loom.

I have included photo before and after fix. I still don't know what the blue wire in the trailer loom is used for. ? where comes from or goes to.

I am attaching photo of my set up - there are 2orange wires in it that are patches/repairs to the original brown and blues wires cut by the auto sparky that I had to reconnect. My heavy red wire is an extension to the P3 red wire, and heavy black wire attached to cut brown wire is the P3 blue wire extension. The sparky cut the brown before the black wire came off, and he fed the P3 blue to the brake loom red wire, and the P3 red wire to the loom's brown wire. No wonder nothing worked - no trailer tail light and Pin5 "funny".
http://www.aulro.com/afvb/attachment.php?attachmentid=60715&stc=1&d=1368969338

I would appreciate sniegy's comments

Rosco

[sniegy]

I fit the diode to all vehicles.

It is there to specifically protect the CJB from feedback. It only costs a dollar at most, so cheap insurance. The stripped end or Kathode needs to go towards the brake controller.

Cheers

[Wayb4u]

Hi,
I am new to this site but found the information already very helpful.
I have a MY13 Discovery 4 TDV6 and I need to have a brake controller fitted for a Jayco Caravan.
I have been quoted $1200 for supply and install a Tekonsha Prodigy as well as an Anderson plug.
Does this sound reasonable for the work involved.??

[discotwinturbo]

Hi, I am new to this site but found the information already very helpful. I have a MY13 Discovery 4 TDV6 and I need to have a brake controller fitted for a Jayco Caravan. I have been quoted $1200 for supply and install a Tekonsha Prodigy as well as an Anderson plug. Does this sound reasonable for the work involved.??

Excessive. $160-$200 for the Tekonsha.
Fleecing and gouging.....
Brett.....

[Meken]

Google for the p3 available from ebay - note the requirement for the p3 to be installed horizontal when looking at the front - and there may not be enough room near your knee due to airbag so you end up with it on the dash somewhere

You should be able to negotiate a better install price from LR dealers. New car I would use LR dealer or authorised service who are experienced.

[Wayb4u]

Thanks,

I though it sounded a lot. I know I can get the unit for $200 max but wasn't sure about the fitting. It wasn't a Dealer quote but a recognised service place.
Anyone know someone in western Sydney that can do the fitting of brake controller that knows all the tricks.