Thread: Trailer socket pin 2 - 7N socket

Cant answer your plug related Q's but you will need resistors and relays for the LED lights so that the disco will detect the trailer.

Originally Posted by loanrangie

Cant answer your plug related Q's but you will need resistors and relays for the LED lights so that the disco will detect the trailer.

I think he’s a D4 owner - so just resistors.

Yep. D4 and all lights working OK. Just mentioned it in case it was relevant. More interested in what pin 2 is used 4. I’ll have some time tomorrow to check further with the multimeter hopefully.

Originally Posted by Ashes

The 7N socket pin diagram is described as below

Trailer Plug info(7 Pin Plug):- Australian Regs:-
Pin1 Yellow Left Indicator
Pin2 Black Reverse/Auxilary
Pin3 White Earth
Pin4 Green Right Indicator
Pin5 Blue Electric trailer brakes/Auxilary
Pin6 Red Brakes
Pin7 Brown Tail lights

I have had to make a adaptor to combine the 7N and 7S plugs into a 12 pin flat socket which I have done and mostly all good!

I have a Breaksafe battery that my caravan manufacturer uses pin2 on the 12 pin flat as the +ve charging source for the Breaksafe battery charging.

How does Pin2 work on the 7N socket.

Is it a signal for reversing lights or an auxiliary 12v feed?
What conditions supply 12v to that pin? I ask this because the LED lights on the caravan aren't letting the car recognise that the trailer is attached as far as I can see

You will need to test the vehicle you use it with to see whether pin 2 is a) reverse light power b) auxiliary 12v output or doing nothing at all

It is wired whichever way it came from factory or whoever fitted it decided what it does.

If it is reverse (on the vehicle) you can disconnect that wire (obviously your caravan isn't using it for reverse) and feed it 12v to charge the breaksafe.

If you have, as I suspect, simply made up a universal connector to suit what's available on different tow vehicles you are out of luck as you can't wishfully assume their pin 2 will be auxiliary to suit you.

You can wire all your own cars sockets to suit your caravan with 12v on pin 2 but not mine thankyou!

You can add load resistors in parallel to your led lights but they get hot so need to be mounted with a bit of thought.

There are LED light load equalizers that are electronic and don't heat up but I have only used them on motorbike blinker circuits.

Some google homework required.

The pin 2 issue won't be affecting anything to do with your car not recognizing the caravan.

Some more testing this morning and I think I have my head around what is required

Pin2 on the 7N provides 12v when the engine is on, headlights on and rear fog lights are on. You can only turn the fog lights on if you have headlights on.

Pin6 on the 7S provides 12v when on accessories/engine on.

For my application I won't alter the car trailer plug wiring, but I will alter the wiring in the 7N/7S to 12 pin flat adaptor that I made. I'm not sure how common it is to change the car wiring but as most of the documentation says it is for reverse lighting so I wont change it but it could be done there.

At the 12 pin flat socket of my adaptor, I will bridge pin9 (comes from pin6 on the 7S) and pin2 and disconnect the pin2 wire at the 7N socket end so I'm not feeding 12v back into that circuit.

This should avoid having to change any of the wiring on the car or van.

Originally Posted by Ashes

Yep. D4 and all lights working OK. Just mentioned it in case it was relevant. More interested in what pin 2 is used 4. I’ll have some time tomorrow to check further with the multimeter hopefully.

Pin 2 as delivered on my D4 was Fog lights from factory

https://encrypted-tbn0.gstatic.com/i...8mAJzmYJE&s=10

Wait a minute my tiny little mind is getting confused.

I don't know what's on the back of a Disco 4 but my understanding in general terms is a 7n is a 7 pin flat socket/plug and a 7s is the large round 7 pin socket/plug

So I was drivvling away thinking you made up a Y connector with a flat 7 pin plug and round 7 pin plug to suit different vehicles and both paralleled into a 12 pin flat socket to suit your caravans 12 pin plug.

I think my advice now that you're getting a handle on it is modify to suit yourself (kinda what I do with everything).

Apologies if I misdirected you.

On the back of my D2 I have wired a 12 pin flat but not used the extra 5 heavy duty pins yet, then have a 50 amp anderson plug/socket through its own breaker for anything that needs 12 volts.

Future mod is to also have a red anderson socket supplying 12v for electronic stability control equipped stuff.

All good. 7n and 7S on my disco 4 are both large round. I’ve made a Y cable to go from the 2 round sockets on disco 4 to a 12 pin flat socket to match the trailer 12 pin plug.