Canbus / towbar wiring Passat B6 estate

[pp241]

Passat B6 140tdi manual estate

Hi is there anybody out there who can help please ??????????????
Like many others I am not prepared to shell out the silly money for a genuine VW towbar & electrics and have gone down the aftermarket route via Towsure. Apart from half dismantling the interior to get the rear bumper off (far easier on my old B5), the towbar was a dream to fit. Even from Towsure the plug-in wiring kit was over £100 (the fixed towbar was only £119!)so I went for their 7 way bypass relay at £26.99.
Now for the question - to save time does anybody know what colour wires to tap into for the tail, brake and indicators. Also I am thinking of tapping into the 12v socket in the boot for the 12v feed to the bypass relay and using an inline fuse (not sure where to put it for easy access but will report back when I've sussed it).
Over to you guys ! ! !
p.s. the plastic threaded studs holding the rear lights in are fragile but good news are only 40p from VW ! ! !

[golfmk5gttdi]

First of all, welcome to the forum.

Can't help with the wiring issue, but if you wish to add some photos of you work etc and also, why not take a read of my towbar research, linked in my sig;)

[PNS2007]

Hi there, you are braver than me in attempting this. I researched this before I had my towbar fitted and contacted no end of fitters both national and small local independants (inc towsure). See my thread in this forum.

You should not need to tap into any wires as the model specific wiring kit should plug in somewhere (so I was told). I would strongly suggest that you do not tap into any wiring from the loom as the vehicles wiring is quite sensitive and uses a cambus type system which should not be touched unless you know what your doing (plse accept my apologies if I'm wrong on this assumption). The passat also uses a trailer stability program which should be activated by a VW dealer which amounts to changing some codes in the engines computer. I personally would be very wary of medling with the electrics as you will void your warrenty and it could cost you a packet. Good luck though and I hope you succeed. Let us know how you get on. Neil

[pp241]

Thanks for the welcome, I did read your towbar stuff - very interesting too. It seems to me that the hardware is the easy bit. I've been fitting towbars to my own vehicles for over twenty years and this is the first one that has stumped me. My trade is an engineer and I worked as a fork truck engineer for 6 years and stayed in the industry after I came off the tools for a further 12 in various roles. Canbus technology came onto lift trucks about 8 years ago, too late for me though. I spoke to a fitter at Towsure in Sheffield who has done a new Passat but his notes are now somewhere in the North Sea ! I am determined not to give up and will post the result !

[pp241]

Thanks for the post Neil, as I said I refuse to be held to ransome by VW who would get my money if it priced the plug in kit resonably. Canbus is not such a mystery as I said I do have a rudementary knowledge just need to have it explained in more detail. I think the system basically uses common wires for several functions and sends different voltages (just a few volts in many cases) to trigger the things connected to them. All the bypass relay does is sense these voltages and with the aid of a 12v supply into the relay sends a 12v output to the relevant function on the trailer / caravan. With regard to the vehicle management system yes you are right re warrenty it could be a problem. My last B5 (130 Tdi sport) had ESP as well but had no way of telling (as far as I know) when I was towing. The one big issue which I can see the need for the management system to know about is the electronic handbrake which possibly would need putting on a little more strongly.
I will let you know if I get through the minefield.
Cheers Paul

[pp241]

Not that it's of much to you now but thought I'd update you on my story. The bypass relay picks up the small canbus voltages to the various light functions and by way of a 12v fused supply routes 12v to the towbar socket and so on to the trailer/caravan/jetski etc etc. Anyway after much tooling around I got hold of a vehicle wiring diagram picked up the relevant wires tapped into the boot 12v socket via a fuse and tested the socket which seemed to work. Flushed with sucess I clipped all the trim in and drove to my caravan storage pound, backed up to it plugged in and kept my fingers crossed - it worked! ! ! The cost of the WK5 bypass relay is £29.00 so I guess it was just about worth the aggro ! !

[golfmk5gttdi]

strangly enough, i've just uploaded a wiring diagram fo the electrics i'll be getting. only 7 pin though. see my latest post in my thread.

[pp241]

Checked it out, same item so can vouch it does work

[pp241]

Photo of 12v power pick up off boot socket

[pp241]

Photo showing how fuse is concealed when cover is on

[pp241]

Photo of fuse before cover is put on

[golfmk5gttdi]

excelent. That has put my mind well at ease. Did you fit you own towbar from scratch?

if so, did it take long, what was involved. and what is your location?

[pp241]

Photo of the 7 way bypass relay & wiring in situ (relay is black box top right).

[pp241]

Yes - bit of a fiddle to get at the bumper screws (interior trim out to get the rear outer light clusters out to get at the top two bumper screws ! ! ! ) and access to towbar securing bolt holes where exhaust heat shield is (can just about bend it out of the way with the rear-most fixing off). Once you get the wiring info sorted the whole job is not that bad. It took me around 4.5 hours actual time but knowing what I do now could do it in 3 to 3.5. Have always used Towsure products and value vs quality is good. Cost for Towbar, ball, prewired 7 pin socket, 7 way bypass relay, plastic ball and socket covers inc vat and next day delivery before 10am £175.00

[golfmk5gttdi]

Hi, ordered my towbar and electrics, Any chance that you noted down the colours of the wires and the terminals they went in to on the relay? I'm assiming you had to take feeds from both rear clusters.

Any additional help or notes that you can supply would be greatl appreciated.

Ben

[pp241]

Hi Ben, Yes will dig them out and post them. I picked up the majority from the offside cluster simply because that is where the 12v feed is. The nearside is used for indicator and side light. Cheers Paul.

[golfmk5gttdi]

Checked it out, same item so can vouch it does work
Thanks, it was on the strength of your post that i ordered my towbar. I'm hoping that VW have used the same colour wires throughout their ranges so that following your advice / guides / instructions should make things a lot easier.

Did you wire up the reversing light or not?

[golfmk5gttdi]

Photo of fuse before cover is put on

what amp fuse did you use?

[pp241]

Hi Ben, The fuse recommended with the relay was 15amp but I think the boot 12v socket is protected by a 10amp so to keep that circuit safe I used a 10amp in the feed to the relay. Obviously I will be keeping an eye on it and will have to pick up a feed to take 15amp fusing if needs be. The wiring is listed below.

Signal Wire from bypass relay Vehicle Loom Wire Colour Location
Yellow N/S Indicator Black Loom to N/S rear lamp
Blue Fog Black/Blue Loom to tailgate
Green O/S Indicator Black/Green Loom to O/S rear lamp
Brown O/S Tail Grey/Yellow Loom to O/S rear lamp
Red Brake Black/Blue Loom to N/S and/or O/S rear lamp
Black N/S Tail Brown/Grey Loom to N/S rear lamp
Grey Reverse Black/Red Loom to tailgate
White Earth Earth Point Wheelarch
(Brown Wires)

Just to confirm my car is an 07 B6 estate 140 TDI

Good luck
Paul

Disclaimer: I am not a qualified auto electrician so anybody attempting to follow what I have done must satisfy themselves that it is ok to do so on their own vehicle. I take no responsibility for any consiquences if it does not work, causes damage or injury to property or person ( or for that matter animal, mineral or vegatable - I'm sure you get what I mean)

[golfmk5gttdi]

Many thanks Paul.
My towbar arrived today and i've got it all spread out in the lounge floor going through the instructions very carefully. It occured to me that i have lights in the lift up part of the boot lid so i'll have to go and see if i can find out if i'll need to locate the wires for them.

One other question, did you disconnect the battery or just pull the fuse for the indicator circuit?:confused:

Many thanks for your help

BEn

[pp241]

Hi Ben, did not disconnect battery or have ign on when I was actually scotchlocking the wires. Also did not put fuse in until ready to test. If you are not 100% then disconnect the battery to be sure. Once you power it all up (the fuse should protect any shorts !)you can test the voltage output at both the output side of the relay and the socket pins (hopefully 12v !) but the indicator buzzer will only operate under load i.e. with the trailer lights connected. I did'nt use the reverse as I only have a single 7 pin socket (the 12N) and the reverse is used on the 12S additional socket (with caravan battery charge and fridge circuits).
Good luck, let me know how you get on.
Paul

[golfmk5gttdi]

My confidence grows yet further.:D

Thanks again.

[golfmk5gttdi]

I now have a tow bar. See this link http://www.vwaudiforum.co.uk/forum/showthread.php?t=13686