How does the connection of a Trailer/Caravan get sensed?

[StewG]

I have a Disco 4 MY13 and just bought a JB Gator Caravan. The electrical connections for lights and RedArc brake controller seem to work ok, but I had to jury-rig a 12 volt feed from the rear power behind LH seat #6 out through the tailgate to Anderson plugs to power the Alco-ESC fitted to the caravan. What I need is two 12 volt feeds to the two Anderson plugs on the van; one for ESC and one for home battery & refrigerator. The white socket allegedly should do this task but I can't find out what is needed to get the two feeds out of this socket. One of the pins is presumed to be a sensing circuit.

This forum has been trawled for all relevant info without finding the precise info I need. There is a lot of good comment and I learnt a lot from contributors, thank you one and all. The Disco rear sensors (in reverse) are driving me mad because it does not disable despite having a trailer attached. The van has LED lights. Should I add a load resistor so that the "lights" draw more current if the sensing is done via the lighting circuit?

Can you explain how it all works and what I could do to, a) get the power to the van, and b) shut up the reversing sensors? [bigsmile1]

[Ferret]

The Disco rear sensors (in reverse) are driving me mad because it does not disable despite having a trailer attached. The van has LED lights. Should I add a load resistor so that the "lights" draw more current if the sensing is done via the lighting circuit?

A pulse is sent down the indicator wiring of the 'black' trailer socket. If the appropriate resistance is detected it assumes a trailer is connected and disables reversing sensors plus enables gear box adaptations. LED indicator lights do not have sufficient resistance for this purpose so the presence of a trailer is not detected. Yes, you need to install at least one load resistor in parallel with the trailer indicator LED lights.

There is a long thread somewhere on it all. Just don't get confused about it all - the D4 behaves differently to the D3. The D4 only requires load resistors, the D3 requires load resistors plus further measures to properly handle LED trailer lights. These differences are not always made clear when people talk about this.

As for power to the van, others can take that up but I think you will find the power lines in that 'white' socket to be not adequate for your needs due to the relatively low current rating of that circuit. Dedicated circuits to the vehicles auxiliary battery maybe required.

[Graeme]

White socket pin 6 is IGN/engine run and pin 4 is permanent supply. Run the ESC from pin 6 and van battery charging from pin 4 although a high current connection is preferable.

[StewG]

Thanks to both Ferret and Graeme. It is all coming a bit clearer. I'll try a few different resistors or globes in parallel with LH or RH indicator wire to ground at the van and see what happens. As for the ESC and Charger, I think I'll remove the original white plug and just run new wires (with in-line fuses) direct from the battery to Anderson plugs at the rear. I've seen a similar arrangement somewhere in this forum. I recently bought this MY13 second hand and it has already had a RedArc fitted and some changes to the wiring at the rear. I'm still trying to figure out exactly what is changed, but the 7-pin black plug seems to do the right things.

[mr_squiggle]

Make sure you check the actual outputs for each of the pins on the 7 pin black plug. My MY13 Disco had a previously installed brake controller but somehow had the brake light & brake pins reversed. I needed to correct the wiring and install the diode that had been missed too.
I ended up having to wire in a Narva 21W load resistor for each of the left & right indicator as well as brake & tail to stop the Jayco van LED lights from flickering as the D4 pulsed the circuits to check the lights.

[dirvine]

I have a D4 16.5. I also have a caravan with LED lights and indicators. I thought I might need the resistance wiring. But I dont. Once I connect the plug it cuts out the rear camera and the sensors. Perhaps the later D4's are wired for LED's just like their rear lights. In regards to wiring up extra 12V. I use the Traxide anderson plug. then I piggy back two extra anderson plugs. one is a red one for the anti sway, one is for the 12V fridge, and one is for fridge detection and the breakaway. I dont use the white plug at all.

[orville]

I have wired up a Caravan, boat trailer and box trailer. The last was the box trailer. I did it because I have a long driveway and when reversing the noise was annoying. I did it in a few minutes. I had some cheap resistors from the net (ebay). I stripped the wire near the left and right indicators. I soldered a resistor green one end and white the other on right side and on the left (other side) yellow and white. This gives the resistance required. Not fancy but works.

[orville]

I have wired up a Caravan, boat trailer and box trailer. The last was the box trailer. I did it because I have a long driveway and when reversing the noise was annoying. I did it in a few minutes. I had some cheap resistors from the net , stripped the wire near the left and right indicators. I soldered a resistor green one end and white the other on right side and on the left (other side) yellow and white. This gives the resistance required. Not fancy but works.

[Chops]

My 16.5 also has a button on the dash to stop the reversing beep, but still leaves the camera active. My beeper goes off as soon as I hit reverse due to the tyre on the back. The camper has LED lights, but we have no problems with them at all, other than two wires being connected to incorrect pins by the installer :bat: thus resulting in no brakes or lights for the trailer. We desired the adapter I use, and now all good. When we get the new van plug put on later, it'll be sorted properly then.

[Disco4Dave]

With my D4, the always-on 12 V supply to the white socket comes via a 15A fuse, which I found to be insufficient for the caravan fridge and battery charging.
I strongly advise running a dedicated power cable directly from the battery to an anderson connector (or similar) for the van. This is what I have now done, using twin 6B&S (13.8 mm2) cable, with a 50A circuit breaker.
The white socket may supply enough current for the ESC.

[veebs]

I was hesitant to mess around with the car's wiring, so instead built my own trailer LED adapter. It's a simple 12 pin male to 12 pin female, with a Narva resistor running from the left indicator pin on one plug to the ground on the other. The whole lot is then reinforced with liberal doses of electrical tape.
This means, when towing a trailer the Disco doesn't recognize, I add this adapter between the trailer cable and the car. Suddenly, no more reversing beeper, the gearbox adapts, and the little trailer indicator lights up. The resistor is out in the wind behind the car, meaning it should stay quite cool too.
If towing something the car does recognise, the adapter stays in the glovebox.

My car came pre-wired with an Anderson plug at the back, which is actually very handy - i used it just this weekend, as i have also wired my air compressor into an Anderson plug (ie, removed the battery clamps). Now, when running the compressor, the bonnet can stay shut, and I simply plug it in to the rear. The old clamps are also wired into an anderson plug, meaning I can still use the compressor direct from a battery if needed.

[veebs]

I have wired up a Caravan, boat trailer and box trailer. The last was the box trailer. I did it because I have a long driveway and when reversing the noise was annoying. I did it in a few minutes. I had some cheap resistors from the net (ebay). I stripped the wire near the left and right indicators. I soldered a resistor green one end and white the other on right side and on the left (other side) yellow and white. This gives the resistance required. Not fancy but works.

Does this mean the car thinks there is always a trailer attached? And at the risk of teaching to suck eggs, does the resistor you used have a heatsink? They get pretty hot, and you sure don't want a potential fire hazard in there!

[StewG]

Thanks to all respondents. I'm experimenting with load resistors to see what works on my D4 MY13. So far I've got the beeping to shut up by connecting 6 ohm 50W resistors across LH indicator, RH indicator, tail-light and reversing connection; a total of 4 resistors. The reversing camera still operates. According to the local Land Rover service agent (Cheltenham, Victoria) it is necessary to fit parallel resistors to the indicators and tail lights; a total of 3 resistors. I'll report back the eventual findings.

On a slightly different topic, the service agent said that for MY13 models, fitting the diode on the braking system is unnecessary (for blocking back-feed into the Body Control Module) because it is only on MY12 and earlier that need that. He also said that the MY16 had entirely different wiring to earlier models and the LED trailer lights were appropriately sensed. LR could sell and fit a black box to overcome LED light (lack of) sensing problem for about $300. The box would include a switch to select whether a trailer has LED or incandescent lamps. I'm starting to think that I should have said yes to that and save all the hassles I'm having...

For what it's worth, the resistors get extremely hot. I'm currently nursing a burnt hand with heat sink stripes across the palm!

[StewG]

In my earlier post today I was adding resistors directly to a bare plug (minus trailer). To make the testing more realistic, I connected up to the trailer (caravan) and added a 6 ohm 50 watt resistor to the LH indicator only. In reverse the beeping shut up, the camera stayed on and I got a little green trailer displayed on the instrument panel for left hand indicator operation. No other effects were noticeable and all lights on car and van worked correctly. Success!

I then fitted resistors to RH indicator and tail lights. Result = similar to before; no beeping, camera works and green trailer displayed on both LH and RH indicators. Success, except for very hot tail light resistor. Decision - put two resistors in metal box on the trailer, each in parallel with RH and LH indicators respectively. Nothing else. Unless someone can tell me a benefit for wasting more power through a tail light resistor, I will not fit it. Indicators are less frequently used and are intermittent in operation resulting in cooler resistors and I am not relying on only one resistor to tell the car that there is a trailer attached.

Incidentally, I found that the "reversing signal" Pin 2 on the D4 black socket is actually an "always-on auxiliary power" outlet - hence the burnt hand previously reported. Note that all the information above is what works (or not) with my specific D4 and JB Caravan. DISCLAIMER - It may be different with other MY13 Disco 4 and other trailers.

[BMKal]

In my earlier post today I was adding resistors directly to a bare plug (minus trailer). To make the testing more realistic, I connected up to the trailer (caravan) and added a 6 ohm 50 watt resistor to the LH indicator only. In reverse the beeping shut up, the camera stayed on and I got a little green trailer displayed on the instrument panel for left hand indicator operation. No other effects were noticeable and all lights on car and van worked correctly. Success!

I then fitted resistors to RH indicator and tail lights. Result = similar to before; no beeping, camera works and green trailer displayed on both LH and RH indicators. Success, except for very hot tail light resistor. Decision - put two resistors in metal box on the trailer, each in parallel with RH and LH indicators respectively. Nothing else. Unless someone can tell me a benefit for wasting more power through a tail light resistor, I will not fit it. Indicators are less frequently used and are intermittent in operation resulting in cooler resistors and I am not relying on only one resistor to tell the car that there is a trailer attached.

Incidentally, I found that the "reversing signal" Pin 2 on the D4 black socket is actually an "always-on auxiliary power" outlet - hence the burnt hand previously reported. Note that all the information above is what works (or not) with my specific D4 and JB Caravan. DISCLAIMER - It may be different with other MY13 Disco 4 and other trailers.

I have done pretty much the same as you have described. I bought a blister pack of 2 x Narva 21W load resistors as below.

https://www.aulro.com/afvb/images/imported/2017/04/652.jpg (https://postimg.org/image/m278dgg07/)

I mounted these together on the side and right at the front of the draw bar on my trailer, and wired directly into the trailer plug - one to each indicator feed and both returning to a common earth.
I have not found that they get hot.
This is all that is needed (in fact, you only really need to use one resistor, wired up to only one indicator circuit). There is no benefit to be gained in adding another resistor to your tail light circuit - the D4 uses the indicator circuit/s to sense when a trailer is connected.

[DiscoJeffster]

Mine hardwired into the camper trailer. As I had two, I connected one to each indictor though as mentioned, only one is required.


https://www.aulro.com/afvb/images/imported/2017/04/651.jpg

[LandyAndy]

Beware that the resistors MAY stop the ECU going to sleep and causing battery drain if left parked for significant time.Our ESTEEMED spannerman/auto elec at work put them on our Merc prime mover after fitting LED lights to correct the indicator speed.You can here a click noise when its parked,the ECU looking for contacts.If its parked for longer than a week it needs a jump start.This may or may not be the case with a Landy ECU.The resistors do get hot!!!!
Andrew

[StewG]

Beware that the resistors MAY stop the ECU going to sleep and causing battery drain if left parked for significant time.Our ESTEEMED spannerman/auto elec at work put them on our Merc prime mover after fitting LED lights to correct the indicator speed.You can here a click noise when its parked,the ECU looking for contacts.If its parked for longer than a week it needs a jump start.This may or may not be the case with a Landy ECU.The resistors do get hot!!!!
Andrew

I can't see how the Disco 4 could suffer the same problem because the purpose of the resistor(s) is to make the LED-lighted trailer look the same as an older incandescent-lighted trailer. The resistors are (ideally) mounted on the trailer and having any trailer connected (say for a week) should not prevent the D4 from shutting down properly and conserving power. However, your warning is heeded and I'll keep a watch on any aberrant D4 behaviour.

[LandyAndy]

I can't see how the Disco 4 could suffer the same problem because the purpose of the resistor(s) is to make the LED-lighted trailer look the same as an older incandescent-lighted trailer. The resistors are (ideally) mounted on the trailer and having any trailer connected (say for a week) should not prevent the D4 from shutting down properly and conserving power. However, your warning is heeded and I'll keep a watch on any aberrant D4 behaviour.

Was only refering to if the trailer was left connected for a long period,say whilst touring.I would be disconnecting,just in case.
Andrew

[shanegtr]

My D3 keeps sending pulse's down to the trailer when shut down. I originally had my LED box wired in with a couple of change over relays that had the trigger wire supply from a ign on 12v. When I turned the engine off my 12v trigger shut down and the pulsing at the trailer LEDS started. Cant recall if it stopped when the car was locked, but from memory if kept going for hours if I left the car unlocked. I ditched the relays after that

[LandyAndy]

My D3 keeps sending pulse's down to the trailer when shut down. I originally had my LED box wired in with a couple of change over relays that had the trigger wire supply from a ign on 12v. When I turned the engine off my 12v trigger shut down and the pulsing at the trailer LEDS started. Cant recall if it stopped when the car was locked, but from memory if kept going for hours if I left the car unlocked. I ditched the relays after that

Exactly what our Merc prime mover does.Having huge batteries means its not such an issue,until its not used for a few weeks.
Andrew

[BMKal]

Exactly what our Merc prime mover does.Having huge batteries means its not such an issue,until its not used for a few weeks.
Andrew

Yeah - but the way that you lot power up accessories on council vehicles - anything is possible. :tease::tease::tease:

https://www.aulro.com/afvb/images/imported/2017/04/537.jpg (https://postimg.org/image/4ko0laamf/)

[LandyAndy]

Yes,I would expect that from our spannerman,and he would tell you how well he fixed it.Normally when he is finished telling us how good he fixed something it fails again.We say,"I thought you said you fixed that".GOLD!!!!!
Andrew

[LandyAndy]

Wet out your way Brian?????
One of my mingions went camping in the goldfields for Easter to Anzac day with his mrs and kids and camper trailer.Was looking good for a good rain.
Andrew

[BMKal]

Wet out your way Brian?????
One of my mingions went camping in the goldfields for Easter to Anzac day with his mrs and kids and camper trailer.Was looking good for a good rain.
Andrew

We got a little bit a couple of days ago - just enough to water the lawns. There has been a bit of heavier rainfall to the north of us - up around Leonora & Menzies - but we didn't see any of that.
Has been great weather here for working outside or in the shed lately - I've been getting a bit done around the place. Just about to order some roofing iron and re-sheet the back half of the main section of the house. [bigwhistle]