towbar wiring on focus

flopsy1973

Hi
i fitted a towbar to my ford focus diesel 57 reg few months back. i have wired it up but have problems with wiring withe brake and tail lights working opposite on each side.
I have followed the wiring instructions supplied and followed wiring on car lamp assembly
I have it wired as follows

TOWBAR CABLE CAR WIRE COLOUR & CONNECTION
yellow yellow audible sensor
blue green/yellow fog lights
white earth
green green audible sensor
brown orange RH tail
red green/red brake
black orange/white LH tail

any help here would be great thanks

Gloomendoom

Swap the offending wires around and see if it solves it?

marlot

Not quite sure what you mean by "brake and tail lights working opposite on each side." but make sure that the trailer bulbs are both inserted the right way around. If not that, then there could be a bad earth, possibly at the bulb.

Start by checking the car wiring, preferably with another trailer, or with a multimeter, then go on to check the trailer.

Joe_Horner

It'll be a fault with the trailer wiring (or a poorly fitted bulb as suggested).

Assuming this is a 12N (7 pin) socket:

First check that the trailer light unit earths are good, clean and tight because bad earths can give all sorts of odd symptoms (though not usually this one).

The car only feeds a single supply to the trailer brake lights (pin 6 / red wire) so, if one of the trailer side lights comes on when the brakes are applied that side light is connected incorrectly. Because there's a single brake feed at the towbar you physically can't mis-wire the towbar itself to cause that symptom.

Say, for example, when you apply the brakes you get left hand brake light and right hand side light then check the right hand light cluster.

If it uses a dual filament bulb then it may be that the bulb's been put in the wrong way (shouldn't be possible but usually is with a bit of ham-fistedness)

If it uses two different bulbs or a single bulb that you're sure is the right way round then swap the wires between the brake and side light connections at that point.

knightstyle

I had this on a trailer with a light bar.
Then I realised I had put the bar on upside down!

flopsy1973

thanks for all that. i have plugged the trailer into a friends car and all works correctly. so i am back to my wiring on car which i have checked again. am i missing something obvious from the wiring i have done supplied on the first post
thanks

Joe_Horner

You simply can't get the fault you're describing by a problem with the car's wiring. Assuming you're talking about a normal 7-pin socket rather than a 13 pin euro style, both brake lights on the trailer are connected to pin 6 on the trailer's plug.

That means that, when power is supplied to that pin, it's supplied to both brake lights. It has to be, because they're connected together to a single supply pin.

If you got the car wiring wrong then you might find that both brake lights came on when, for example, you put your right indicator or your fog light on, but - if the trailer wiring is good - then both brake lights must come on together when power is applied to pin 6 of the socket.

A bad earth on the trailer might cause what you're experiencing, in which case it may well have made good contact in between trying it on yours and trying it on your friends. Same with a poorly fitted bulb if it uses dual filaments - if loose it might vibrate and make different contacts at different times but a bad earth on your car wiring wouldn't - that would just prevent any of the trailer lights working reliably.

pappa_golf

flopsy1973 wrote: »

thanks for all that. i have plugged the trailer into a friends car and all works correctly. so i am back to my wiring on car which i have checked again. am i missing something obvious from the wiring i have done supplied on the first post
thanks

does your friends trailer work on your car? , I would suggest that you have connected the tail light and stop light up incorrectly on your socket


try swopping the wires over

Joe_Horner

pappa_golf wrote: »

does your friends trailer work on your car? , I would suggest that you have connected the tail light and stop light up incorrectly on your socket


try swopping the wires over

That can't do it.

there are two connections in the socket for tail lights (7 for left, 5 for right) and a single connection for brake lights (6). That means you could swap (5 and 6) or (7 and 6).

If you swap 5 and 6 then, when you put your brakes on, the trailer's right hand brake light will come on all by itself. When you put your side lights on the left side light (fed by correctly wired pin 7) will come on, and both brake lights will come on as well, fed by incorrectly wired pin 6.

If you swap 7 and 6 then the same thing will happen, but on the other side (brakes give right side, sides give left side and both brakes.

Even if you got all three wrong (say, wired brakes to 5, left side to 6 and right side to 7) you'd still get both trailer brake lights coming on together because they're wired together on the trailer