Thread: D4 not detecting trailer wiring

Thanks for the clarification.

So that means for the Disco 4 I need 4 resisters. One on each of the indicators, brake and tail light. The box would need to be large enough to hold 4 resisters.

Given that's all that's in these magic boxes you can buy why do they cost $200 plus ?

Originally Posted by dannog

Thanks for the clarification.

So that means for the Disco 4 I need 4 resisters. One on each of the indicators, brake and tail light. The box would need to be large enough to hold 4 resisters.

Given that's all that's in these magic boxes you can buy why do they cost $200 plus ?

Because people like me who have NO IDEA about vehicle electronics and general electrics for that matter wouldn't know how to wire one up.

If you're happy to put one together that works I'll pay you the money instead.

Originally Posted by dannog

Thanks for the clarification.

So that means for the Disco 4 I need 4 resisters. One on each of the indicators, brake and tail light. The box would need to be large enough to hold 4 resisters.

Given that's all that's in these magic boxes you can buy why do they cost $200 plus ?

You only need them on the indicators.

You can get away with just a single resistor on one of the indicator circuits only. This is enough for the vehicle to sense that a trailer is connected, and will stop the reversing beepers continually going off when in reverse etc but it will only show the flashing trailer indicator on the dash for that same side indicator. To have the flashing indicator on the dash working for both side indicators, you need to put a resistor in both indicator circuits on the trailer.

Thanks guys I can hardly believe its that simple. 2 resisters on the trailer and its fixed. Cheers

Originally Posted by Peteren

Just a note on the resistor units from FoMoCo, they don't work on a D4.
Ordered one and tried it, no luck.
Opened it up and found the resistors are 120 Ohms, nowhere near enough load for the D4 to detect a trailer connected.


Got a couple of Narva 21 watt resistors and rebuilt the adapter, it now works fine

I just want to say a big thanks to Peteren (and the wider AULRO Community) for posting this photo solution to the D4 LED Caravan lighting issue.

(I was also amazed at how little information I could get from official LR outlets when making enquiries about a fix for what is sure to be a fairly widespread issue)

Anyhow, based on the photo above and information in this forum, I made my own version of the Resistor Indicator Module (RIM©) for my 12 pin plug set up.

Each resistor runs from the +L & +R in the 7 pin round to the -ve in the 7 side of the 12pin flat.

Hook her up, shut the LR 4 door, indicators flash, trailer detected.

(Yes, with this set up the car will detect a trailer with only the harness plugged in, but I never drive like that, so it's not a problem. Plus, this way I can connect any trailer with LED lights and the harness will do it's job)

The Resisters are simplybolted to the square metal tubing, keeping them away from plastic/rubber/wiring etc.

$40 for the resistors and a fun half day making it all up and testing and making it look neat.

Thanks again!
unnamed-1.jpg

Originally Posted by CBurgo

I just want to say a big thanks to Peteren (and the wider AULRO Community) for posting this photo solution to the D4 LED Caravan lighting issue.

(I was also amazed at how little information I could get from official LR outlets when making enquiries about a fix for what is sure to be a fairly widespread issue)

Anyhow, based on the photo above and information in this forum, I made my own version of the Resistor Indicator Module (RIM©) for my 12 pin plug set up.

Each resistor runs from the +L & +R in the 7 pin round to the -ve in the 7 side of the 12pin flat.

Hook her up, shut the LR 4 door, indicators flash, trailer detected.

(Yes, with this set up the car will detect a trailer with only the harness plugged in, but I never drive like that, so it's not a problem. Plus, this way I can connect any trailer with LED lights and the harness will do it's job)

The Resisters are simplybolted to the square metal tubing, keeping them away from plastic/rubber/wiring etc.

$40 for the resistors and a fun half day making it all up and testing and making it look neat.

Thanks again!
unnamed-1.jpg

I do like that simple mod for the resistors.
Can I ask a question about your wiring to the 12 pin plug please?
Did you use heavier wire for the higher current pins from the white/grey 7 pin plug? Or did you go with normal trailer wire??
Thanks
Alan

Hi Alan,

Yes, heavier gauge wire on the white plug for the fridge hot wire, Trailer brake away battery (Only) and earth. (I dont use this plug for Auxiliary batteries, using a separate anderson with 6 B&S instead)

I think 8 B&S from memory. (Cant remember exactly, but pretty sure it was that.

Biggest wire I could fit in the terminals of the 12 Supplementary plug.

Hope that helps

This seemed like a solved issue so after reading the forum I bought two 21w Narva Resistors and put them in (one on each indicator wire / yellow and green ) and yet my MY15 Disco doesn't recognise trailer attached still.... urgh. Indicators and everything working as expected but no green trailer light on dash... Any ideas? Do I need to wire in 4? Do I need to wire them differently to make them work... Other seem to have fixed the issue with less hassle?