Towbar Wiring - S211 - Help please!

[Timster]

Hi.

I fitted a towbar this weekend, but am having trouble with the electrics.

I'm trying to do it via a bypass relay, but getting no signal through to the socket however I try. Through reading I'm led to believe it's possible, but beginning to doubt it - can anyone shed any light on whether they've done it sucessfully?


I'm very tempted to order the dedicated wiring kit, but this needs coding to the vehicle - is this something that I'd need STAR to do, or take it to a star enabled centre, or is there a plug and go option witha dedicated kit?

All help greatly appreciated!!

 

[Druk]

Can't help with the bypass but don't opt for the Westfalia wiring if you go that route. The cables sizes are inferior for UK towing; imho of course.

The 212 wiring kit I fitted worked straight out the box for the basic functions but needed coding to eliminate the rear foglights/parking sensors when hooked up. And coding required it connected to Germany . However, maybe that's the 212 only

Speak to PF Jones. http://www.pfjones.co.uk/mercedes-2008-on-7-pin-westfalia-wiring-kit-313361300107.html




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[Timster]

Cheers for that.

I've bought everything through pf Jones and am waiting for a call back from one of their advisers as they assure me the bypass relay should work.

Great company - can't fault them for their customer service.

It's a witter bar I've bought!

 

[dozypillock]

Cheers for that.

I've bought everything through pf Jones and am waiting for a call back from one of their advisers as they assure me the bypass relay should work.

Great company - can't fault them for their customer service.

It's a witter bar I've bought!

I went for the proper one for mine in the end. I was informed that by law you have to have notification of a bulb out on the trailer etc
It seemed easier to have it all done by the car, instead of a beeper fitted to tell you when you indicate. Also, some cheap bypass kits can play havoc with the canbus, flagging all sorts of spurious warnings. I decided I would rather not risk screwing up the cars electrics, as the correct one, coded, was only about £100 extra, if I recall.

Neil

 

[Timster]

Thanks all - so after a chat with the technician at PF Jones (Can't praise them enough again for their customer care and after sales advice) It would appear that someone forgot to connect the earth for the trailer supply


Doh - Guilty as charged!
Will have a go again tonight once the kids are in bed and report back!!!!

 

[pipmk]

I went for the proper one for mine in the end. I was informed that by law you have to have notification of a bulb out on the trailer etc
It seemed easier to have it all done by the car, instead of a beeper fitted to tell you when you indicate. Also, some cheap bypass kits can play havoc with the canbus, flagging all sorts of spurious warnings. I decided I would rather not risk screwing up the cars electrics, as the correct one, coded, was only about £100 extra, if I recall.

Neil

P F Jones are a very reputable company who would not retail a product that did not comply with the law, (if only for fear of legal consequences if nothing else). I can see no legislation that trailer has to have bulb failure notification. Most cars lack this so it would not work on them anyway.

A "proper" one is any which complies with the legislation.

 

[Druk]

P F Jones are a very reputable company who would not retail a product that did not comply with the law, (if only for fear of legal consequences if nothing else). I can see no legislation that trailer has to have bulb failure notification. Most cars lack this so it would not work on them anyway.

A "proper" one is any which complies with the legislation.

Could the legislation possibly be that a trailer indicator needs to 'beep' in the cockpit if connected and that this can be circumvented by having a bulb failure warning instead? Mine certainly doesn't beep but does say if it isn't working.

 

[dozypillock]

Could the legislation possibly be that a trailer indicator needs to 'beep' in the cockpit if connected and that this can be circumvented by having a bulb failure warning instead? Mine certainly doesn't beep but does say if it isn't working.

That is exactly what I was told. I think it has been like that for years. Interestingly, the system in my other towcar has the annoying beep system, but I do not believe it would warn me if side or tail lights fail?
The coded merc system should, I believe, tell me of any bulb failure.

Neil

 

[pipmk]

Could the legislation possibly be that a trailer indicator needs to 'beep' in the cockpit if connected and that this can be circumvented by having a bulb failure warning instead? Mine certainly doesn't beep but does say if it isn't working.

I get a louder "tick" when the caravan is attached and the bulb failure system works for the van. The rule has always been that you either had an audible confirmation of the indicator working or an extra indicator light. I do not know if a bulb failure system would circumvent this necessity. I think it would have to be tested in court.

 

[davidjpowell]

I get a louder "tick" when the caravan is attached and the bulb failure system works for the van. The rule has always been that you either had an audible confirmation of the indicator working or an extra indicator light. I do not know if a bulb failure system would circumvent this necessity. I think it would have to be tested in court.

Most new cars work on the bulb out system now. I honk it must be firmly established that they must Notify of a fault either by a message when faulty. Or show a audible/visual signal when working.

Our car has the message, and showed the fault on tail lights rather than indicators when someone let the cable drag....

 

[Timster]

Update:

It all works. A massive shout out to PF Jones who gave me technical support over the phone this morning, and didn't laugh at me when it was suggested the fault was the distinct lack of earth in the cable going from the relay to the plug socket - my own stupidity, and I'd been so careful!

So: For anyone interested -

Witter Fixed Flange Towbar from PF Jones £93.
I wanted fixed flange as I have a bike rack that fits on this style and can be used while towing.

Fix wasn't too bad, big job taking the bumper off, but assembly of the bar was straightforward. Several rusted bolts to remove after 12 years and 220000 miles, but with the right tools came off easily. All in all to fit the bar was about 6 hrs work including setting up and tidying up afterwards.

Wiring in the bypass relay - here's how I did it:

Power to the relay - find a 12v unstitched feed and an earth - connect the bypass relay, I put an inline fuse 10a in for extra measure.

Break into the wiring harness running along the nearside of the boot floor after removing the trim. It's the biggest one, shrouded in black tape running towards the back of the car.

I don't like scotch blocks so once I was sure which wire was which I soldered and heat shrunk my connections which were as follows:

Wire from relay - Wire colour in harness
LH index - black/white
RH index - Black/green
Brake - Green / yellow
RH + LH rear lights - black / red
Fog light - blue /green

Then connect the 7 pin plug to the relay - straightforward but - DON'T FORGET TO EARTH IT!!!

Test it
Tidy wiring
Replace boot lining
Go for drive

Enjoy the fact you've a) done it yourself, b) saved £130 on the MB dedicated wiring harness


Just been for a 20 mile drive to ensure all works and it's all working perfectly. The E320cdi S211 pre-facelift with the inline 6 engine makes for a beautiful towbar with my small folding caravan!

 

[Timster]

For those interested here's my rather unique caravan! Bought for next to nothing about 6 years ago, and restored to the point where it's a dry comfy shelter for family adventures. We almost sold it a few months ago due to lack of towbar, but decided we couldn't part with it!!!

https://www.youtube.com/watch?v=E0OyyfvhfxY&feature=em-upload_owner

 

[Timster]

ALSO - I did some research on legality.

It seems DJPowell is correct here:

If the dash has a warning when connected to a trailer / caravan etc then there is no need for an audible buzzer, however if no warning on dash an audible buzzer should sound!

 

[Dickie Fix]

ALSO - I did some research on legality.

It seems DJPowell is correct here:

If the dash has a warning when connected to a trailer / caravan etc then there is no need for an audible buzzer, however if no warning on dash an audible buzzer should sound!

I did some research on this recently as, unlike all my previous cars, the factory-fitted towbar electrics on my new B Class has neither a separate audible or visual tell-tale when a trailer is connected. The Owners Manual has this to say:

“Towing a Trailer
If LED lamps are fitted in the trailer, an error message may appear in the multifunction display even if there is no fault. The reason for the error message could be that the current has fallen below the minimum of 50 mA.
To ensure reliable operation of the bulb failure indicator, each LED chain in the trailer lighting must be guaranteed a minimum current of 50 mA.”

So the manual seems to imply that the trailer’s indicator lights become integrated with the car’s bulb failure system, thus meeting any legal requirements for a tell-tale.

This extract from a Caravan Club information leaflet about towbar wiring seems to confirm that view:

“It’s a legal requirement that the towcar ‘shall be equipped with an operational tell-tale for front and rear indicators (including any rear indicator on the rearmost of any trailers drawn by the vehicle)’ (Road Vehicle Lighting Regulations, 1989.) This is sometimes referred to as the ‘C1’ and ‘C2’ functions (‘C1’ refers to the telltale for the car’s indicators – C2 is the extension of that function to the caravan). This tell-tale can be audible or visual. Some show the correct functioning of the indicators, perhaps via an instrument panel light or boot-mounted buzzer. Others operate by altering the standard flasher function to an alternative ‘warning’ signal if a fault is detected. This latter option is in essence an extension of the car’s built-in bulb failure monitoring system, and is increasingly the most common option especially with vehicle manufacturer-supplied wiring kits, and vehicle-specific aftermarket wiring kits. Note that this tell-tale function is sometimes neglected when the towbar wiring is fitted – this is illegal. Do check with your system supplier as to how the tell-tale functions, however, before assuming the C2 function has been ignored – some owners expecting a separate warning light or buzzer have been surprised to learn they have a function integrated into the car’s bulb failure warning system instead.”

 

[Druk]

The above might imply that a bypass system doesn't have the integrated failure warning that a dedicated loom offers. Tim...does the bypass then have an audible or other system?

 

[Timster]

The above might imply that a bypass system doesn't have the integrated failure warning that a dedicated loom offers. Tim...does the bypass then have an audible or other system?

Hi. Yes, the bypass relay also has a built in buzzer which buzzes (beeps) every time an indicator is activated.

I took a bulb out the indicator on my caravan to see what happened and the buzzer didn't buzz so as long as I'm hearing a buzz when I indicate all is working I guess (i always check the rear lights and brakes before setting off)