Trailer brake lights (1 Viewer)

[Chickie]

The brake lights on my trailer do not work. All other lights work, I have tested the continuity on the trailer all is correct, when i plug the 7 pin socket into the car every light works except the brake lights on the trailer, I have bought new sockets for car and trailer new bulbs still dont work. Reading it may be a fuse I have looked at all the fuses are ok do any of you know where the fuse might be on a Citroen Berlingo multi space 2004. I am at a total loss.

 

[icantremember]

Have you checked the output at the socket on the car?

 

[Landy Andy]

You can quite cheaply by tow socket testers. They test both male and female parts, and is something I always use to test before I test anything else.

I can’t see there being an individual fuse just for towbar brake lights. They will be supplied by the same supply as the vehicles brakes, and by a canbus relay live if fitted, but if the relay fuse had gone other lights would be effected.

 

[Speve]

I had a similar problem and discovered there were two fuses on the tow bar controller in the vehicle battery box one had blown and I was missing the left hand lights
We have a small black electronic box sitting on top of the battery.

 

[Spriddler]

The brake lights on my trailer do not work.

Is this something new? (We are assuming that they used to work but have now stopped working).

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[dunnah01]

Is there 12v at pin 6 (10 o'clock) when the brake pedal is pushed?

 

[Chickie]

Yes checked the output socket on the car all good. I took my car to a mates house to test his trailer his lights did not work so it must be my car, I even have a spare battery so I connected +& - to socket points all 7 individualy all worked including the brake lights, I have been racking my brains for 4 days now. Having a glass of wine now so try again tomorrow. Thanks for reply's but please keep them coming in I need my trailer.

 

[Chickie]

Both the red wires are at 10 o clock looking at it from the back of the car.

 

[GeoffnDee]

If you do not have a canbus system ,It could be a poor connection at the point that the brake light supply is picked up , or a faulty cable. (allowing some voltage through but not enough amps to power the brake light bulbs) . You could try a separate cable from the brake light power supply at the rear to the trailer socket to check this.

 

[pappajohn]

If it has a canbus bypass box it could be the brake light relay has failed.
Other than that it can only be a break somewhere in the main loom to socket wiring as the vans brake lights work..

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[LithiumConvert]

Bad earth connections can produce all sorts of hard to diagnose faults.

 

[Chickie]

Thanks for all your help I have just started working on it again and found the problem it is the new 7 pin plug, the brake terminal cross was not open enough i put a screw driver in it opened it a bit, and hay presto the lights work. 5 days of racking my brain for a simple thing. est la vie