7 pin tow bar socket wiring.

[littlespark]

I’m swapping over the tow bar from one vehicle to another identical one.
All fairly straightforward, colours are all correct.
The query I have is, Will the 12v aux socket in the back of the van have enough power to run the relay box?
The towbar was originally fitted by a dealership, and that’s where they took power from, ive I’ve not had any problems.
Just wondering if that’s normal or I should it be directly from the battery (in-line fuses already on the cable)

 

[Strima]

More than enough, all you're doing is powering a couple of lamps.

 

[telectrix]

More than enough, all you're doing is powering a couple of lamps.

and 2 of them are on/off, on/off. like my mate aked me to check if his indicators worked. i said yes/no, yes/no......

 

[littlespark]

Yeah. That’s what I thought, but I looked up the wiring diagram for the relay box and it wanted a 15A fused supply cable which splits into a 10A and a 7.5A both going into the relay box. I think an aux socket is only 10A

I’ve got this to connect up before I ply line the back of my van

 

[Strima]

Box probably asks for 10A for caravan charging socket?

 

[ruston]

Usually the auxiliary socket is 15 amps. Check the fuse box legend.
I have fitted loads of them through the relay without any problems.
Just ensure your connections are good lol. Scotch locks in particular, if you would use them.
As said , only in extreme circumstances will you have brakes, sides, hazards , and maybe a fog light, or two on together for any duration.
Two rear fogs, would be borderline with that lot at 12 volts , but with engine running would be fine ..

PS. Tap into the wiring lol, don't use a plug . I know you won't plug it in , but just mentioning to save comments .

 

[littlespark]

Ok... got everything wired up, but not getting anything out the relay??
Theres a multiway plug for all the inputs... and testing these are all giving some power. (don't know if its exactly 12v though... just using my voltage detector 2 prong tester)
connections to indicators are right... they go on/off/on/off... (thanks tel for that!)
Might not have brake and reverse lights right, because I cant check them on my own... it was a 50/50 guess, and if its wrong, easy to swap over.
The relay has a plug for the inputs, and screw terminals for the outputs... and im not getting any voltage on them at all. (Testing between each terminal and chassis)
Would there be a need for a citroen dealer to do something with the van computer as I believe its a canbus wiring system....
but then, I wouldn't be getting anything at the inputs??
Ill test at the actual socket tomorrow, but i plugged the trailer in this morning and got nothing on the trailer lights.
I will also use my multimeter on the inputs and see if im getting 12v or not.

Relay unit is a Ring RCT485 Smart Logic which was fitted with the towbar originally by a citroen dealer, and this has just been moved over onto my new van

 

[ruston]

The canbus is bypassed by the relay , the relay is triggered by the respective tap into the lighting harness ,then the auxiliary lights are powered by the auxiliary feed from the external 12 volt supply. The canbus does not see this and does not react as a fault.
Ps , a good earth to the aux lights is critical.
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Have they used the dedicated harness plugs for the existing van , or have they tapped into the harness ? If they have used the plug in harness it should be straight forward . The system I described is an after market relay.

 

[littlespark]

I'll have to check the old van.
I've tapped into the cables just before they go out to the tail light cluster.

 

[ruston]

This is the relay that I normally use . They are reliable and easy to fit.

 

[littlespark]

I had a bad earth for the relay. works now.
had an issue with the right hand indicator, but I guess that what happens when I reuse the old connectors.

so that's it all boarded back up, better not be another fault

thanks for the help