Thread: Discovery 3 LED trailer lights

Originally Posted by But 'n' Ben

I conclude that, although the Automatic bits of Magic are Enabled/Disabled, when only one Load is fitted, it requires both indicator circuits to have a load fitted in order to get the green trailer indication.

Don.

If (for some reason) you need both indicators to illuminate the trailer icon, then yes, you will need a resistor across both indicator circuits. However, in all other functions one is enough (it's a latching circuit, not an instant "toggle").

Cheers,

Gordon

would you guys know if a 12v 40amp resistor protected relay work? The resister is inbuilt between poles 85 and 85. Dont know the resistor value. in the relay

mudgee

Unfortunately, no. Well the relay will work OK, but you still need the load resistors. The internal resistor is to protect the vehicle circuit boards and is not really seen by the signal light system load sensing circuits.

The resistance of the internal resistor across pins 85 and 86 for a nominal 12VDC relay is most often 680 ohms. On some relays the resistor is either not there at all or replaced by a diode.

The purpose of the resistor is to soak up voltage spikes that can result when the power to the coil returns to zero - that is depowered. The energy in the coil has to go somewhere, the resistor soaks it up rather than a printed circuit board in some onboard computer.

These voltage spikes can harm the computers within a vehicle and that is why most relays on newer vehicles now incorporate some sort of spike dampening or absorption design feature.

thanks bbyer looks like i'll go the other way

mudgee

Originally Posted by Colin Pedersen

Hi all,
Here’s a diagram of the basic wiring to stop the pulsing on a LED trailer.
Simple and easy to make using either crimp connectors, soldering or fitting into a transportable box if needed.

A suitably rated transistor would also work well but a little more complex in the circuitry but would remove the click click of the relay operating.

Originally Posted by Cappa

Question - what impact does the do nothing " option have to the car? I mean apart from the twinkle of the indicator lights and the rear sensor never stopping - what else stops working on the D3?

I like the idea of adding auxilary set of globes to provide the necessary load.

thanks !!

Rather than "Stops Working", it is more of a case of what remains in operation.

When the 3 senses that a trailer is attached, the rear distance sounders are disabled as they would see the trailer when reverse gear is selected. Also automatic height changes at speed are inhibited if the trailer is sensed, no sensing, no inhibition. There may also be some gear shift point changes as well but of that, I am not certain.

I'm helping a mate tow a car from Melbourne back to Adelaide this coming weekend. He's borrowed another blokes race car trailer which has LED lights. It also had a rectangular light connection so I needed to get an adaptor.
I had a spare load resistor from when I fixed my trailer lights so I got to work on this.
ImageUploadedByTapatalk1388919061.368985.jpg

I extended the wiring so that I could hang the rectangular plug off the hitch pin/bolt and added a load resistor into the indicator line as required. I'll test it out in the morning but I'm happy with the outcome assuming if works!

Cost was less than $25.

Looks similar to what I have done.

7 pin plug & socket gets connected inline between the trailer & the car, with a little box housing the resistors in the middle.

Picked up a twin pack of the resistors from Autobarn for $10, and the metal box from Jaycar. Already had the plug & socket.

I have only used one resistor, as the box was a little small for both, but all the lights work well. FWIW - I put it in the right indicator cct, and the dash light flashes when I indicate right, and not left, as I expected. But, the main thing is, the left indicator on the trailer works as it should.

Cheap, simple & easy... bit like me, really...