c5 towbar

[scas]

hi, i got a secondhand towbar for my wifes 06 c5 saloon with the wiring and ,i think , a relay that bolts behind the lining in the boot and plugs into the citroen wiring loom. to cut a long story short the horsebox lights arent working. i checked the pins on the plug and while there is power, no circuit seems to have more that 1.2 volts.
i took the socket of my spare parts c5 and when i got to changing it i noticed there are about 11 wires in the plug from my wifes car and the usual 7 in the donor car. 3 of the wires go to some sort of sensor that tells if a trailer is attached-but theres at least one other. on the socket there are 4 extra very small pins that all have about half a volt in them, around the usual 7.
is this wiring for a caravan or something?

[GiveMeABreak]

I think it's going to be impossible for us to answer this without knowing what wiring loom you have (make and part numbers) and some pictures. There are lots of different ones out there - but they must be compatible with the car's electronics - you can't just stick any old one on and expect it to work. The Citroen ones are also designed to work with the car's ABS / ESP system (where you have ESP fitted) to provide a different programme for towing wither a trailer or caravan. There is usually a trainer unit board that handles all the wiring loom connections and then the trailer fusebox unit interfaces with the car's loom to the BSI.

[scas]

Thanks. The loom and towbar came from an identical c5. Same year even.i now have a different problem. When i gave up the car was beside the horsebox. I started it and parked it where it usually sits. Went out 3 hours later and it wont start. Throwing up braking fault and gearbox fault and the starter doesnt turn. Also no head/dip lights or front indicators and front sidelights. I did the bsi reset a few times but with no luck. Obviously i disconnected the box that all the trailer connections go into but still no joy. Hmmm

[scas]

Ill take some pics soon. Also at no point did i disconnect a single wire from the socket at the back for the trailer

[GiveMeABreak]

Check all the fuses - if you’ve misconnected something or connected a wrong wire it can cause issues with the BSI under the passenger glovebox. I would suggest you double check your battery terminal connections and make sure the battery is not flat as a first step.

[scas]

Thanks. Batterys making 12.6v. All the fuses in glovebox and engine bay are fine. Its dark so i cant really tell where its coming from, but theres a constant humming/buzzing from the engine bay somewhere below and to the left of the ecu. Maybe i fecked a relay

[scas]

the old feker runs again. gearbox was locked, brake fault, both airbags faulty, everything ahead of the bulkhead didnt work, horn, radio, and electric seats were all not working. the first thing i had done was to check every fuse. went back to it a couple of days later and decided to do it again, the first fuse i pulled was the little 5am one for the trailer socket, again it looked fine, replaced it with a new one and everything worked.
citroens really do wreck yer head sometimes. btw where are the relays-i couldnt find one anywhere?
so the wiring loom that i got from the breakers must be a bit feked-can anyone point me in the direction of a loom for a facelift c5 hatch 05 2ld auto on the internet, i found some but they all seem to be 150 euros.

[GiveMeABreak]

The relays on these cars are incorporated into the BSI (the main computer in the glovebox) They are generally not the type you can easily replace unless you are an electronics whizz.

So which wiring loom are you after there are loads - and also your VIN will be needed to get the correct part diagrams for your C5.

[scas]

so if a relay blows do you replace the whole bsi unit? im looking for the loom for the trailer socket, ill did out the vin later when i get home-thanks

[scas]

for a 7 pin socket

[GiveMeABreak]

It depends - some models may have a few relays for specific functions like the glow plug relays, but most are handled by the BSI and these are soldered onto the board itself.

I can only provide you with the recommended towing harness part numbers for your specific vehicle - the car options will mean they can differ depending on equipment. I'll see what comes up when you get the VIN later.

[beelim]

Have you put in the 30amp fuse in the glovebox. I was stuck for hours with the same problem until I took a photo of my other c5 with a towbar to compare. And have you told it with Lexia that it has a towbar. In Leixlip with a Lexia if you need help.