12N Towbar Wiring Question (T25 Estate)

[David Bell]

Hi there, I'm mid installing a towbar to my Avensis estate (2008 T25).

I'm only towing a small trailer tent, with basic lighting (brake/side/indicators)

I've been reading about the Bypass relays and have actually bought one (on the off chance the car needs it).

But having read this

Toyata Avensis T25 "Twin Electrics / 12S" wiring diagram

http://www.toyota-tech.eu/legacy/Toy/aimuploads/%7B178FB06F-72F6-4E1F-BA9C-1E7251820FDB%7D/TB%20WH%2012S%20PZ417-T5560-00.pdf

and this

Toyata Avensis T25 "Single Electrics / 12N" wiring diagram

http://www.toyota-tech.eu/legacy/Toy/aimuploads/%7BAE84ECB1-247B-4534-9BF4-23EB87C32011%7D/TB%20WH%207p+%20PZ417-T5563-00.pdf

From what I can gather I only need the bypass relay if I am doing the full 'twin' electrics - ie the 12S shown in the first PDF.

The 2nd PDF makes no reference to taking a power feed from the Battery, and just shows the Toyota wiring loom and a in dash LED for showing the indicators working.

I've got the towbar installed and the 7 core wires from hitch into boot, but am about to tackle splicing them into the loom, I know which wire goes where, and would much prefer not to have to bother running 12v from Battery to boot.

Cutting out the relay would also lose the buzzer facility tho, so i'd buy one of those seperately (take it that's a legal requirement, as I'd prefer not to bother?)

Can anyone else confirm this would be ok?

It's a T25 diesel estate from 2008.

Thanks,

David

[TyphoonTerry]

Hi David.

Try looking at this link http://www.towbarsrus.com/bar-tow-wiring.htm

It may help.

Rgds

Terry

[A-Harris]

I am desperate for help on this topic too, but none of the above links are working.
Does my Toyota Avensis estate t2 D4D, T25 2007, 2 litre have multiplex wiring or not?

I need to order a wiring kit and am not sure whether to order an 'N' type or an 'S' type,

...or whether I need the by-pass relay system or not.

I will only need it to power a trailer board.

Thanks if you can help.

[Heidfirst]

"I am desperate for help on this topic too, but none of the above links are working."

Go to http://www.toyota-tech.eu/Aim/Aim.aspx?pubtype=AIM&menuitem=2

select Avensis, 2006/4 MMC Gen 2, Installation Manual & select Towing Hitch Wiring Kit

[Mike169]

I used to fit towbars for a living, if you are only towing a trailer then it is the 'N' socket needed, think of it as 'Normal' the 'S' is 'Supplementary' which includes wiring for fridges, charging points, etc, for a caravan, hope this info helps?

Mike.

[A-Harris]

"I am desperate for help on this topic too, but none of the above links are working."

Go to http://www.toyota-tech.eu/Aim/Aim.aspx?pubtype=AIM&menuitem=2

select Avensis, 2006/4 MMC Gen 2, Installation Manual & select Towing Hitch Wiring Kit

Thanks for pointing the guidance. Sadly I have visited that page many times and still cannot find any guidance on Tow Hitch Wiring. I have downloaded all the manuals for fitting towbars, but can not find any reference to wiring at all. :o(

[A-Harris]

I used to fit towbars for a living, if you are only towing a trailer then it is the 'N' socket needed, think of it as 'Normal' the 'S' is 'Supplementary' which includes wiring for fridges, charging points, etc, for a caravan, hope this info helps?

Mike.

Thanks for that info Mike 'N' for normal, I like that and shall remember it. Now I just need to know whether its a multiplex system and or whether mmy Avensis needs the bypass relay or not ?

Any thoughts?

[Mike169]

Hi Adrian, ok i 'used' to fit towbars, probably about 2000 over the years and cars were less developed then but i still worked on a few state of the art models so to speak but i am unsure what you mean by needing a bypass relay for a multiplex system? All we used to do was to find the loom where it entered the rear area and before it separated between the two rear lights and attach the say 2 metres of 7 core cable of the towbar 12N socket and 'splice' it, using Scotchloks and connecting the wires accordingly.

Yellow n/s flasher, blue fog light, white earth, green o/s flasher, brown n/s side light, red brake lights and the centre black n/s side light....hope this helps.

Mike169 https://www.google.co.uk/search?q=12n+wiring+diagram+socket&tbm=isch&tbo=u&source=univ&sa=X&ei=ksVdU-_LIYfFPcP3gbAM&ved=0CC4QsAQ&biw=1024&bih=673

[A-Harris]

Hi Mike thanks for that great link on wiring, it will be very useful.

Until about 25 years ago I was in the motor trade and used to fit the occasional towbar when required, but have recently been warned of difficulties due to the changes in how modern cars are wired and have no personal experience of modern wiring systems which report back to the central computer.

I am under the impression that bypass relays are necessary on some car models to prevent expensive to reset/fix computer fault codes appearing. Due apparently to the rear light wiring now only carrying small currents and the current draw being constantly monitored. But like I say, I have no idea or personal experience with these systems. The other concern is that if the system is multiplexed (I gather many french models are) that single wires carry the current and a mutiplex single informs 'smart light' clusters which bulbs to switch on!

I don't know if Toyota were doing this back in 2007 when my Avensis was made?

Not Toyota, but a friend tried fitting a front suspension strut to a modern Audi - exactly the same model - and the car refused to work. The onboard computer reported that this part was not officially fitted to that car and refused to let the car start.

Scary isn't it!

As the cheapest I can get a dealer fault diagnosis is around £175 just for plugging it in - without correcting any faults - you can see why I am being a bit cautious. Maybe I should just throw caution to the wind and do it with fingers crossed :o)

.

[Mike169]

Hi Adrian.

How about giving these guys a call, Towrite 01708 223316, 0845 5214508, just a shop i know but they know their stuff. If he still works there a guy called Geoff knows the trade inside out.

You could make a casual enquiry making out you want a towbar fitted and ask them if the wiring is straight forward or do they wires they connect interfere with the cars ECU/computer/bulb safe system, just chat to them and mention the multiplex system and get their reaction as they will know up to date stuff that might of overtaken me now. (P.S. don't mention me, lol)

Mike.

[MVWTRD]

Done single N socket today on my 1.8 vvti 2004 T25 estate. Wire colours as follows:

Socket                              car

Yellow (LH indicator) to green with white stipe

Red (brake lights) to thick green with white stripe with silver dots

Brown (RH tail light) to green

Green(RH indicator) to green with yellow stripe

White (earth) to white with black stripe

Blue(rear fog light) to red with white stripe

Black(LH tail light) to  green

Saves anyone else after this information a few hours. 

 

 

 

[Chileanmadman]

Just made an account to say THANK YOU! Been searching for ages for color specs!!