Trailer light question

[jackkyxu]

That seems like a low of draw. What resistors did you end up using? How/where did you add them in? I think I am going to have to do the same as you.

i am also interested in what resistors to buy

this is the one I found, with criteria as 10 ohm, 20 Watts power load (should be 15W, but I give some tolerance, better safe),

there are a lot of resistor types; looks like Metal Oxide Film Resistor is the one which can stand the heat

 

[Steven Hill]

I did some searches before writing this, so I apologize up front if this question has been asked. I hooked up my trailer wiring harness this weekend so I could pull a 19ft boat. Would have had the dealer do it, but they couldn't fit me in. I know I still have to go back for the programming. My brake lights and signals work fine, but the tail lights don't come on. The boat dealer said the lights all worked, although I never noticed since everything was done during the day hours. I checked the fuses and the ground and all are good. The trailer does have LED lights and I am wondering if this is the issue. I will hook it up to a friend's truck tonight to see if they work as designed, which should point to something in the LR4. If it is due to the LED tail/side lights, is there a simple solution? Thanks in advance for any help.

SOLVED!!

Hi all so i had the exact same problem on my Discovery 4...let me explain what was wrong on Venter Savuti XL trailer with LED lights and how i solved it.

This is what was wrong and actually a very easy fix, it takes 10min

Indicators worked on trailer
Brake lights worked on trailer
Running lights did not work on trailer
Trailer sway and stability assist was not working on the car as it was not sensing the trailer, and PDC's kept going nuts when in reverse.

I went to have a relay box fitted at a tow bar fitment center and it just helped the running lights but nothing else...do not go this route!!! As it still does not activate land rover stabilty and towing safety features.

After reading through the forums i went to GT electronics in Boksburg and purchased two 10ohm 25watt resistors and placed them on both the trailer indicator lights IN PARALELLE!!!! NB!!!! VERY NB!!

I put back the original trailer wiring from land rover and removed that ****** little relay box...it will not work with that relay box, you have to remove it.

put everything back to original only the resistors in trailer and BOOM!!!! Car now reads the trailer is connected and runnings lights also working.

Basically the LED lights on trailer or whatever it is you may be towing have too small a load to "sense" that there is something connected.

Installing 2 resistors increases the load and...fixes all problems. 10ohm 15w will also work just fine but i used 10ohm 25w as the electronic store did not have any stock of 15w resistors.

You can just buyvthe resistors and have the dealeship or any service center install them for you, they will insulate them propery and mount them for you.... cost me $6 or R90 south african rand....and also very easy to do yourself....10min

You will know it is working when you indicate.... the green trailer icon on your dash will flash on and off with your indicators, put you car into reverse and PDC should automatically be switched off.

Done and dusted. Hope this helps everyone. And thanks for your help too.

Please see attached wiring diagram...must be installed in paralelle......NOT SERIES...

 

[BeemerNut]

With 12.6 volt typical vehicle system voltage your around 16 watts or app 55 BTU/Hr heat generated at the power resistor. Mount it in an open area allowing heat dissipation and not up against anything. Any 25 watt power resistor will run a lot cooler than a 15 watt unit costing more plus larger overall size......~~=o&o>.......

 

[LR4USN]

I was looking at this... https://www.etrailer.com/Wiring/Curt/C57003.html

but someone in the comment said that it doesnt work with an LR3. So... not sure.. but that adapter is what I want.

As of July 1, 2023, the Curt adapter still doesn't work on Land Rovers, my 3rd time in 3 years buying and returning hoping they made improvements.

 

[ftillier]

I tried it too, even measured across all the pins with my multimeter and there is no resistance there. I ended up buying a magnetic incandescent trailer light (for putting on the trunk lid of a car you might tow with a dolly) that uses the 4-pin plug to help the car detect there's something there, with the trailer (and it's brakes) connected using the 7-pin plug. Works well, looks a bit janky.

 

[BigBriDogGuy]

I mentioned this issue when I went to the local trailer shop and they plugged in their pigtail testing unit into my 7-pin. The pigtail was about 10 feet long so he could go up to the controls by the driver's side door and test everything while he was reading the tester. He said "Everything seems to be working fine." I said, "Even the brake controller?" He said, "Yep." I said, "What about LED lights? I heard there is a problem with LED trailer lights because they don't send enough juice through the system for the trailer wiring to pick it up." He said, "Aren't your tail lights LED?" I shrugged my shoulders and said, "Not sure. But, if they are, that's a good point."

Not saying that this known problem isn't a problem, but if the tail lights are LED, why would LED trailer lights be a problem for the system to recognize?

 

[ftillier]

The LED lights on the trailer work, and all signals go to the connector so trailer brakes should too (since those are controlled by the add-on brake controller), the car just doesn't detect the trailer. Whether that makes a difference is debatable, some have said that the trailer sway stuff works regardless, but maybe that's just standard stability control. Seems like it would benefit from the car knowing there's a trailer to adapt. If you get a trailer icon when the turn signals blink, then the car detected the trailer. Otherwise, it didn't detect it, but everything still largely functions. Without knowing how the stability control is actually programmed it's hard to tell. We're just black-box testing.