Towbar Wiring

[Zeus]

I have just the bought a new Eupoean style towbar, with regard to the wiring I have read on this forum that I need to buy a harness that conects back to the BSI behind the passenger side glovebox.
I was wondering if it is possible to splice onto the existing rear tail light wiring and connect to the 7 pin trailer adaptor; if unable to do so is anyone able to let me know where I can get the harness?
Any help would be helpful.

 

[simca1100]

1. What model of Peugeot, what year?

2. My understanding...
You should NEVER splice to the existing tail lights if the car has multiplexed* wiring, this is very risky - if there is ever a wiring short in the trailer, (and that is common enough) the car's multiplexed electrical system could be damaged - possibly requiring the replacement of the body computer... if your car is an older one, it might even be uneconomical to repair, it may effectively write off the car...!

That is the advice I have read on the issue for many years, but... When I bought my 307 wagon new in 2007, I had a genuine Peugeot Australia tow bar fitted by the dealer. They should have used the Peugeot trailer lights module, but they didn't... Many years after purchase, I fitted (non-genuine) rear parking sensors myself and as part of that operation, traced the trailer plug wiring... which went straight back to the tail light units, no interface module was fitted at all, not genuine Peugeot and not even a generic. Very bad practice but the dealer had closed down by the time I discovered. I had the car for 10 years and never had any problem with the trailer wiring, but it was still dodgy of the dealer to install it that way. From memory the correct interface module was priced at around $300 new.

Multiplexed wiring - this means that the lights (and other devices) are NOT directly switched by the dashboard controls, but the controls simply send a signal to the car's body computer, which sends a digital signal to a remote module somewhere else in the car to switch the light (or other device) on or off. Everything is switched by the computer, not by the dashboard switch.

I'm not an expert, the above is my lay person's understanding.

 

[seasink]

The necessary electronic module can be bought, but it is easily home made.

You need four relays, one for tail lights, one for brake lights, and one for each side indicators. They draw very little current and shouldn't disturb the computer's sensing. Each relay is connected to the appropriate light backplate and to a common earth, switching a 12 V supply. A non-bus source for the supply has to be found, usually at a cigarette lighter socket. 10A suitable relays are cheap. Put them all side by side on a small circuit board, and preferably colour code the wiring from the lamps to the trailer plug.

Use low ohm coil or electronic relays (electronics shop), not automotive ones, to keep the current draw increase minimal, otherwise the BSI will complain.

Years ago there was a lot of discussion of this in AF, with diagrams and details. If you want functions beyond the lights for a light trailer it gets more complex.

 

[Zeus]

1. What model of Peugeot, what year?

2. My understanding...
You should NEVER splice to the existing tail lights if the car has multiplexed* wiring, this is very risky - if there is ever a wiring short in the trailer, (and that is common enough) the car's multiplexed electrical system could be damaged - possibly requiring the replacement of the body computer... if your car is an older one, it might even be uneconomical to repair, it may effectively write off the car...!

That is the advice I have read on the issue for many years, but... When I bought my 307 wagon new in 2007, I had a genuine Peugeot Australia tow bar fitted by the dealer. They should have used the Peugeot trailer lights module, but they didn't... Many years after purchase, I fitted (non-genuine) rear parking sensors myself and as part of that operation, traced the trailer plug wiring... which went straight back to the tail light units, no interface module was fitted at all, not genuine Peugeot and not even a generic. Very bad practice but the dealer had closed down by the time I discovered. I had the car for 10 years and never had any problem with the trailer wiring, but it was still dodgy of the dealer to install it that way. From memory the correct interface module was priced at around $300 new.

Multiplexed wiring - this means that the lights (and other devices) are NOT directly switched by the dashboard controls, but the controls simply send a signal to the car's body computer, which sends a digital signal to a remote module somewhere else in the car to switch the light (or other device) on or off. Everything is switched by the computer, not by the dashboard switch.

I'm not an expert, the above is my lay person's understanding.

It's a 2005 407

 

[simca1100]

Will be multiplexed.

These days probably easier to buy the correct electronic module out of a wrecked car than make one up from relays and circuit board.

If the car has reversing sensors, these are automatically disabled when a trailer is plugged in, IF the right module is fitted.

If a generic or no module is fitted, this doesn't happen and the sensors go off because "something" (the trailer) is behind the car.
On my 307 I had to fit a manual switch in the boot to disable the parking sensors when trailer was connected.

 

[bob]

If the car has reversing sensors, these are automatically disabled when a trailer is plugged in, IF the right module is fitted.

just discovered last week that the factory towbar fitted by Essendon Renault to the Kangoo doesn't switch out the sensors, the reed switch terminals in the trailer socket are empty.... and also has the turn indicators swapped over !! Naturally, the wire colours used have no relationship with what the rest of the world regards as standard....

Time to browbeat the dealer, they haven't answered my email of last week - supply and fit was $1363.64, so not a cheap exercise, ordered prior to delivery in my silly belief that it would be done correctly via a dealer....

A mate had his Koleos towbar fitted by Ballarat Renault - they screwed the socket to the plastic bumper instead of the provided point on the towbar !

Bob

 

[LynCliff]

Hayman Reece make a unit that can be spliced into the tail light wiring with a chip in it which isolates the connection to the cars can bus system.
It is about $150 as a kit or $300 fitted from Hayman Reece dealers. I had one fitted to my 2014 508 just recently at Ballarat trailers and Tow Bars and it actually works good. It had been fitted with a Peugeot one which did not work on Led trailer lights.
They also had a loan car to use while we waited to have it fitted.

 

[Peter C]

This is interesting. Just recently, when replacing one of the left hand tail light globes on my D9 406 sedan, I noticed that there is an unused wiring loom which is terminated by a plug, located in the wheel well, behind the left hand wheel. Could this be for a trailer connection?

 

[LynCliff]

Most likely would be, it is on the 508, have not looked at a 406 yet

 

[COL]

These modern tow bars can be bought separately or with a wiring kit. If you don't have much electrical knowledge you would probably be better of getting a wiring kit and follow the installation instructions that come with it. this way it should be just plug and play.

 

[JAJEA]

I also chose to have an original Peugeot tow bar fitted by the dealer to our 508GT Wagon on the belief that it would be done right.
The cost around "bob's" figure ~$1300+ and it is an original EU 12 pin plug with an adapter for the flat 7 pin plug.
The installation is supposed to cater for conventional filament and LED globes.
Just like "bob", I'm going to find out when the time comes to tow. I hope I don't have to browbeat the dealer because they're no longer there.

The dealer had quite a bit of trouble following Peugeot's installation instructions and delivery was delayed as a result.

 

[COL]

I also chose to have an original Peugeot tow bar fitted by the dealer to our 508GT Wagon on the belief that it would be done right.
The cost around "bob's" figure ~$1300+ and it is an original EU 12 pin plug with an adapter for the flat 7 pin plug.
The installation is supposed to cater for conventional filament and LED globes.
Just like "bob", I'm going to find out when the time comes to tow. I hope I don't have to browbeat the dealer because they're no longer there.View attachment 238225
The dealer had quite a bit of trouble following Peugeot's installation instructions and delivery was delayed as a result.
View attachment 238226

If your concerned about if the wiring is correct, go to your local trailer hire place or borrow a friends trailer and plug into the trailer and test to make sure they have wired it correctly.

 

[COL]

If you have a multimeter or a 12 volt tester you can easily check the wiring at the socket.

Here is a link to nice easy to follow colour coded diagrams of all the different trailer plugs & sockets available in Australia

Australian Trailer Plug and Socket Wiring Diagrams | Trailers R Us Australia

Australian Trailer Plug and Socket Wiring Diagrams - Technical Guides Australian Trailer Plug and Socket Wiring Diagrams

www.trailersrus.com.au

 

[Haakon]

This is easy, just use a bypass relay box. I’ve used this on a bunch of multiplex Renaults and the Alfa. Splice into the existing feed to the tail lights and it pulls a tiny current that the body ECU won’t notice, and you give it a power supply feed. Easy peasy.
Some versions of these sort of things will even decode signals like I have on the Alfa where the brake and tail lights are supplied by the same wire and it’s a modulated signal the taillight itself decodes.

Towbar Electrics 7 Bypass Relay to fit Jaguar Negative Switch Trailer Caravan | eBay

Easy to wire, if you can wire a towbar the old fashioned way you can wire this unit. The wires from the relay are connected directly to the back of the vehicle lights as with normal tow bar wiring to provide a signal to the relay.

www.ebay.com.au

 

[Zeus]

Thanks all, I sure have some thinking to do, might be a while before I am able to start, I will try a few of the differnt ways and see what happens.
Cheers

 

[Zeus]

This is easy, just use a bypass relay box. I’ve used this on a bunch of multiplex Renaults and the Alfa. Splice into the existing feed to the tail lights and it pulls a tiny current that the body ECU won’t notice, and you give it a power supply feed. Easy peasy.
Some versions of these sort of things will even decode signals like I have on the Alfa where the brake and tail lights are supplied by the same wire and it’s a modulated signal the taillight itself decodes.

Towbar Electrics 7 Bypass Relay to fit Jaguar Negative Switch Trailer Caravan | eBay

Easy to wire, if you can wire a towbar the old fashioned way you can wire this unit. The wires from the relay are connected directly to the back of the vehicle lights as with normal tow bar wiring to provide a signal to the relay.

www.ebay.com.au

Hi Haakon OF Dune,
I have decided to Get the TEB7AS Relay negative switch.
I dont want to stuff up the wiring could you walk me through fitting the relay.
The attchments are of the boot fusebox.
Thank for your time.

 

[Haakon]

I’m not familiar with 407s so you’ll have to work it out I’m afraid. Tap into the wires for stop, tail, and indicators at the tail lights, and then find a switched feed in the fuse box of an appropriate amperage.

You can use piggyback fuse adapters for the power feed.

 

[DoubleChevron]

I’m not familiar with 407s so you’ll have to work it out I’m afraid. Tap into the wires for stop, tail, and indicators at the tail lights, and then find a switched feed in the fuse box of an appropriate amperage.

You can use piggyback fuse adapters for the power feed.

if you don't using the correct wiring harness, you will need to use an isolation circuit. They should be easily found on ebay UK. Its basically a small black box that has a bunch of mini-relays in it, so you don't load the factory circuits with extra loads (and mess up any load drawing sensors etc....). I just run a power wire under the car upto the underbonnet fuse box (from memory).

Why did you have a Euro connector fitted? I would fit a standard 12 pin australian trailer plug to everything these days. You can also plug the 7pin flat connectors into them. so no converters are needed. if you ever come across a trailer/caravan with a 12pin socket, it will also plug in.

seeya
Shane L.

 

[seasink]

As well as the rear cigarette lighter, some 407s have a boot fusebox. For these F3 is a 15A rear accessories fuse.

Shane, your box is essentially the same as the cheap DIY method I posted.

 

[Haakon]

if you don't using the correct wiring harness, you will need to use an isolation circuit. They should be easily found on ebay UK. Its basically a small black box that has a bunch of mini-relays in it, so you don't load the factory circuits with extra loads (and mess up any load drawing sensors etc....). I just run a power wire under the car upto the underbonnet fuse box (from memory).

Why did you have a Euro connector fitted? I would fit a standard 12 pin australian trailer plug to everything these days. You can also plug the 7pin flat connectors into them. so no converters are needed. if you ever come across a trailer/caravan with a 12pin socket, it will also plug in.

seeya
Shane L.

No? Really? Huh.