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Here's a conundrum. ..
I have a trailer with working lights and two vehicles (one british one french)

The lights work with both vehicles, EXCEPT FOR ONE RIGHT HAND RUNNING LIGHT - off the FRENCH vehicle(citroen dispatch 2001).

The lights on the french vehicle are not connected through the right hand set of rear lights to the towbar electrics -only via the left-hand set.

BOTH running lights work fine on the trailer from the UK vehicle.

So I decided the trailer wiring must have two inputs, one to each side.

One brown one black? Im not sure how to test for that.

I don't want to interfere with the French vehicle lights.

I have checked the french vehicle earth.

Can I simply run a wire across in the trailer, to connect the two sides of the running lights together?

Or can I join them up somehow very simply via rearranging the pins?

Its all Greek to me

I want to be sure it will still work on both vehicles if possible.
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Hi Shippi , from memory when this happens on our trailers it is because the pin for the non working side has not made contact in the plug . Maybe the Citroen plug is only fed from one side and just needs linking on the female , vehicle side of the plug ?
  • Thread Starter Thread Starter
  • #3
Hello JD6400 thanks for replying.

I have checked the pin plug on the vehicle.
The right hand vehicle rear lighting block is not connected to the vehicle trailer towbar female socket. Only the left lights are connected.
  • Thread Starter Thread Starter
  • #4
How would I link the two up? I'd have to run an extra wire from the right hand vehicle running light to somewhere along the wire from the left hand one.
Would this interfere in any way with the car relay wiring or controls?

I was rather hoping to avoid that by not messing in the car at all and changing the wiring on the trailer side. I realise more power will be going thru but thats ok there should be enough as they are only LEDS.
Sounds like you just need to link the pin for the RH light to the pin for the LH light in the trailer socket on the citroen. If there is nothing currently connected to the RH pin then it wont interfere with anything else on the vehicle.
  • Thread Starter Thread Starter
  • #6
There is no right hand pin. Because there is no connection from the right hand light unit at all, to the trailer socket in the vehicle. The lights are only connected to the towbar socket via the left hand set of rear lights.
So if I add one wire from the right hand light block, I need to know if joining these two running lights together will harm any relays. Are you sure? I dont mind if not, I'd prefer not to bother unless I am confident of not doing damadge.

I prefer to know if it can be done on the trailer side. So, in effect two lights just run off one pin (the one already connected and working)
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I think you are missunderstanding. If I understand correctly, there is a connection from the left hand light in the vehicle to the pin for the left hand light in the trailer socket (pin 7). There is nothing connected to pin 5 for the RH light. If you link pin 7 to pin 5 in the vehicle, then the left hand vehicle light will power both trailer lights.

If you link the 2 pins together on the trailer side, then it will link the 2 lights together on your other vehicle.

What you should really do is link from the right hand light in the vehicle to pin 5 to maintain 2 seperate circuits in case one fails, but depending on the vehicle you may then need to add relays (but if the left hamd light is wired direct to the trailer socket you should be able to do the same with the right)
  • Thread Starter Thread Starter
  • #8
Yes we are both misunderstanding each other.
My diagrams dont show a separate pin for each of the running lights. and they arent numbered, Just coloured. Only the indicators have separate pins.

I suppose what I now need to know is that no.5 pin will likely be corresponding to "black". [I could double-check the position of it by testing which pins are live with the driving lights on on the uk vehicle.]

Brown = running lights
Black = accessories
Blue = fog
Yellow = indicator
Green = opposite indicator
White= Earth
Red = brakes
  • Thread Starter Thread Starter
  • #9
:) It has to be the black, doesnt it! ;)o_O
  • Thread Starter Thread Starter
  • #11
Ha ha! All these pins and circuits.
Makes me think its all far more complex than it probably is!. I dont think I understand relays much at all.

Thanks so much for untangling my spagetti :)
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