Merc Tow bar issue

Discussion in 'Tech/Mech General' started by Arty, Sep 6, 2013.

  1. Arty

    Arty Read Only Funster

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    Hi all, just bought myself a Merc Sprinter 2011 Mwb with the rear step
    I need to fit a tow bar so I can tow my boat, I like to do trail aways for fishing as this is my hobby
    I thought this shouldnt be too difficult to fit my own towbar as I did so before on my VW Transporter
    Well it seems things have moved on and now I have to have a vehicle specific wireing kit VSE whereas I had an universal set up in the T5 and now this comes into the MOT test also so no way round it
    I think the idea is to ensure all towing vehicles will have on dash monitoring of trailer tail light bulbs
    Personally I always check my lights whenever I hook up so not sure what all the fuss is about??
    Anyways Ive come round to the idea of VSE and thought that would be an end to it but then i'm told a VSE kit won't be compatible with the LED lights on my trailer! I can't catch a break here and i'm certaintly not ditching my LED's as i'm really chuffed with them, much brighter and more reliable almost industructable and even waterproof
    So if anyone can advise on a solution here I would be very grateful, one other thing is that I read that I need to protect the ECU in my van from faults on the trailer? How do I do that?

    Thanks for any help

    Arty.
     
  2. pappajohn

    pappajohn Funster Life Member

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    Hi Arty, you are part correct regarding the towing electrics.

    if you use a 7 pin socket then it is NOT an MOT point

    a 13 pin socket is a testable item but has nothing to do with bulb failure warning.

    there is nothing to stop you using a universal CanBus bypass relay kit but it does mean tapping into the existing wires....really not an issue if you use decent connectors.

    the dedicated wiring kit comes with OE plugs and sockets so unplug from the lights and plug in the new harness then plug the other end of the new harness into the original harness which you unplugged off the lights.

    LED trailer lights....no problem.

    the bypass relay is powered directly from the battery, not the lighting wires, and the lighting harness connections only trigger the various relays which are then connected to the input wire from the battery.
    the relay triggers WILL NOT effect the canbus wiring so no faults shown on the dashboard.

    end of the day, a universal kit does the same thing, may take longer to fit but is maybe £100 cheaper.
     
    Last edited: Sep 6, 2013
  3. Geo

    Geo Trader - Funster

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    me thinks his worry is the LEDs wont draw enough power to trigger any indicator repeater/ warning system
     
  4. pappajohn

    pappajohn Funster Life Member

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    doesnt matter....

    even a dedicated loom wont trigger any dash warning lights if a trailer bulb fails, whether filament or led, as the trailer lights are fully isolated and independant of the vans original lighting circuits.

    as i said before, the dedicated harness is just a means of connecting the relay box without having to cut and splice the original wiring.

    the original lighting circuits only trigger the various relays, a very light load and undetectable to bulb failure system, which in turn connects the trailer lights directly to the battery, or fuse box.

    a single positive wire feeds all the trailer lights with the various relays deciding which trailer light is lit

    as for indicator repeaters and buzzers, they to are powered by the battery as the relays click in and out powering the trailers indicators
     
    Last edited: Sep 6, 2013
  5. Johns_Cross_Motorhomes

    Johns_Cross_Motorhomes Trader - Motorhome & Accessory Sales

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    Now where else would you get such precise and informative knowledge freely available on such a friendly forum.:thumb:

    Peter
     
  6. TheBig1

    TheBig1 Funster Life Member

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    if the load sensing circuit doesnt detect that the trailer is plugged in, add an LED ballast resistor. even with a bypass relay kit fitted, the can-bus will detect the presence of a trailer light circuit and will show this on the dashboard to verify indicators are working
     
  7. Arty

    Arty Read Only Funster

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    Wow! You guys have offered more useful help in a few lines than I have had over the past few days from various suppliers! Thanks:thumb:
    I spoke to Towquipe with regards to a Witter fixed flange bar that comes with just about every electrical kit you can think of !
    My plan was same set up as my T5, universal relay fed straight from the battery earthed on the chassis, I believe it senses the voltage in the relevant wire on the vehicles tail lights and then powers the trailer lights

    This system worked very well on the Transporter and was really easy to install and reasonably priced too, the system I had before was Westfailia and used to give an audiable beep when turning, I imagine that was a requirement?

    So you guys are saying that I can have A "7 pin" set up with either VSE or universal electrical kit (bypass relay) and this will work and be legal?

    So it would seem that with a 7 pin set up the only benifit to having a VSE loom is ease of fitting and I would imagine some improved installation quality
    That said I think I found the plug to connect to "under the rear step" and I can imagine it being like a monsoon under there in rainy conditions dirt muck everything being throw up from the road! :rain:But the the plug will always be there whether I connect to it or not, mmm, I still like the idea of making my own connections soldered and heatshrunk easy peasy

    No pun but I think Towquipe must have got their wires crossed and thought I wanted a 12 pin set up??
    Started quoting the "LAW HAS CHANGED, NOW YOU MUST DO THIS"
    I have to say in six years no mot tester even looked at my towbar on the T5 but then it was 7 pin
    Ok so I'm making progress! And this looks to be a great forum:thumb:
    :thanks: you guys
    Arty.
     
  8. Arty

    Arty Read Only Funster

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    Good tip! The T5 worked with the bypass relay and my LED trailer lights so fingers crossed with this Sprinter van:pray:
     
  9. Johns_Cross_Motorhomes

    Johns_Cross_Motorhomes Trader - Motorhome & Accessory Sales

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    Now all you need to do is Subscribe best tenner you will even spend:thumb:

    Peter
     
  10. Arty

    Arty Read Only Funster

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    :Wink: your not wrong, might even be able to get some fishing in if I can get this tow bar fitted.
     
  11. pappajohn

    pappajohn Funster Life Member

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    my 7 way bypass kit came with a built in buzzer AND a terminal to connect to the dash trailer telltale...if the dash has one, not all vehicles do.
    but it still wont detect a blown bulb as it is powered independant of the failure system

    a warning system, either. visual or audible, is a legal requirement....and is part of the MOT for 13 pin, but not a 7 pin.

    personally, i would never fit a 13 pin setup....6 more connections with the potential to fail...and would convert to 7 pin if the trailer came with 13 pin

    one other thing i always do....

    wire the n/s vehicle tail light to the o/s trailer tail light.

    that way, if the fuse for one side blows you still have a tail light on each side....one on the trailer and one opposite on the van
     
    Last edited: Sep 7, 2013
  12. Arty

    Arty Read Only Funster

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    I have a great system for checking if a bulb is out, walk round the back of the trailer and see if they are working:RollEyes:
    I can't change a bulb when i'm driving along so not sure what is the point of a warning system
    I you are towing then you have to take an even greater responsibility and consider other road users even more, I want people behind me to know whats going on well in advance of any manouver I may be making and thats why I have LED lights and I always check them and they always work!

    Rather than a system to warn you of bulb failiure make sure to the best of your ability that they don't fail, thats my aproach.
     
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  13. pappajohn

    pappajohn Funster Life Member

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    pity you cant teach a few farmers and builders in that train of thought.

    how many times have you followed a trailer with one brake light flashing in unison with the opposite indicator due to poor earths ?
    or worse still...farmers with no lights except the rotating beacon spinning away with no lens or bulb. :Doh:.
     
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