Thread: Discovery 3 LED trailer lights

Originally Posted by otobas

I know this thread was a while ago now, but I took your tip and built a pig-tail with a box in it containing the requisite bits and pieces. It works fine for suppressing the pulsing lights and driving the blinkers on my Disco 3, but the vehicle doesn't recognise the trailer being there. I think that might be because I used a ceramic resistor in place of the LR12s (cheaper), but chose the wrong one (probably not big enough).

Do I HAVE to use the LR12? If not, what value resistor should I use?

David P.

You have to have the resistor in parallel with the lights. The system looking to recognise that a trailer is attached will be looking for a 21W bulb.

Power = V x I

I = Power/V in our case I = 21/12 approx 2 amps.

V=IR or R = V/I in our case R = 12/2 = 6 ohm. nearest readily available values are either 5.6 ohm or or 6.2 ohm. Just make sure that the resistor is able to handle the 20 Watts.

I have a 2013 Freelander 2. I recently replaced the lights on my old trailer with LED units and found that the vehicle no longer recognized that a trailer was attached. There was no trailer icon showing on the dash, the reversing sensor squealed all the time and presumably the stability control algorithms were compromised. After reading this thread and a bit of head scratching I fitted a single LR12 load resistor between the earth wire and the right hand turn indicator - problem solved!

It occurs to me that there may be a lot of people out there who are unaware of this problem. If you are towing a trailer and the trailer icon does not show, then it is probably best to disable the stability control until a suitable load resistor is fitted.

No, it's not best to disable DSC. It is still effective, even when not primed for a trailer.

Cheers,

Gordon

I'm with Gordon - I wouldn't be disabling dsc particularly with the trailer on. That computer is still a lot quicker at correcting (dare I say even smarter) than me - especially as the years and distractions build

I used my little adaptor yesterday towing the car trailer from Adelaide to Melbourne. All of the lights worked except for the clearance lights. No problem as we were coming over in the day.
Turns out that we can't leave for home tomorrow till midday. We need the clearance/tail lights for the last few hours coming into Adelaide.
Painfully, the clearance lights work fine on a Toyota but no luck with the D4. Seemingly, the D4 has a wiring issue.
I ended up wiring the clearance/tail lights (brown wire) into the white plug on the right of the tow hitch. From what I can see, it's the green wire which I think is an auxiliary wire.

It looks terrible but I guess I'm safe that way. Is there any issue with using this power source?

If your clearance lights are not working on the trailer, are the tail lights?

They should be wired in parallel on the trailer, so regardless of what vehicle you attach the trailer to, they should work.

But, doing it the way you have should be ok. The white plug just supplies power, and nothing else, as far as I am aware.

I take it you have your magic box wired in with the indicators on the trailer?

Yes. No tail lights. Brake lights fine.
Load resistor on the left indicator.
As long as I'm ok using the power source from the white plug with no issue.
The reason I ask is after rooting around with it yesterday for half hour with the LED headlights on and the doors open , I had trouble starting the car. I'd push the start button and the screen would say the entertainment system would shut down in 3 mins if the car wasn't started, then the whole thing just went dead. We pulled out the trailer plug, and additional wire, gave it a few minutes then it started like nothing was wrong. Just one of those things I guess. If we stop on the way home I may just pull the additional wire out. I only have 1 battery.
Off topic sorry. Thanks for the reply.

Originally Posted by slug_burner

You have to have the resistor in parallel with the lights. The system looking to recognise that a trailer is attached will be looking for a 21W bulb.

Power = V x I

I = Power/V in our case I = 21/12 approx 2 amps.

V=IR or R = V/I in our case R = 12/2 = 6 ohm. nearest readily available values are either 5.6 ohm or or 6.2 ohm. Just make sure that the resistor is able to handle the 20 Watts.

Knuckled down and just bought the LR12s in the end - it now works a treat! Thank you so much for your advice!