A Bizarre problem with bleeper reversing lights

Discussion in 'Motorhome Chat' started by Scattycat, Jan 22, 2015.

  1. Scattycat

    Scattycat Funster

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    I've recently bought some replacement reversing bulbs that when engaged give out a bleep as well as lighting up.
    They work fine on our little Clio but on the camper the light works but no sound.
    I've checked the voltage at the light clusters on both vehicles and they are identical.
    Any suggestions as to the reason?
     
  2. Jonkil

    Jonkil Funster

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    How new is your camper?
    Modern CAN Bus systems hate voltage fluctuations and can be very fickle.
     
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  3. Scattycat

    Scattycat Funster

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    Our van is a 2008 Rapido, the Clio is a 2004
     
  4. pappajohn

    pappajohn Funster Life Member

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    Could well be canbus.

    Anything other than the expected resistance in a particular circuit will cause the canbus to shut down until the extra load is removed.

    Nothing you can do about it.

    Even LED bulbs won't work unless they are canbus compatible
     
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  5. Scattycat

    Scattycat Funster

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    Canbus? Never neard of it. so, what exactly is it?
     
  6. TheBig1

    TheBig1 Funster Life Member

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    CANBUS is in effect an electrical system controlled by a dedicated controller/computer. amongst other things, it measures the current drawn by each light circuit so can tell when a bulb fails or is the wrong type
    far more complicated than that though but its only a broad description to explain your issue
     
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  7. pappajohn

    pappajohn Funster Life Member

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    It's a clever, single wire system to control lighting primarily.

    Just one 12v wire feeds a control centre which receives low power signals to each lights control switch.
    The signal triggers individual electronic relays and diverts power from the single 12v power wire to each light on that circuit.

    It saves having a heavy wire going from switch to light in every circuit thus saving resources.
    One heavy feed wire and a dozen lightweight trigger wires instead of a dozen heavy wires.

    The downside is the trigger wires are load sensitive and only work at the correct resistance....your buzzers are altering that resistance.
     
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  8. Jonkil

    Jonkil Funster

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    Even wire length is pretty critical..... Lengthen the wire and it may not work.
    CAN Bus uses a system of "nodes" to control circuits..... To be honest it's a pain in the arse to diagnose sometimes.
    New generation CAN Bus is even more complicated, thank goodness I'm retiring and selling up this year !
     
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  9. Charlie - Minton

    Charlie - Minton Funster

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    Think my old Transit connect (2010) used something similar to this.
    I fitted a tow bar but the lighting board would not indicate correctly:(
    Ford dealer said he would re map the ecu for 70 quid due to the extra bulb :rolleyes:
    I just removed the side repeater :LOL: it worked fine then(y)
     
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  10. pappajohn

    pappajohn Funster Life Member

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    Fitting towbar lighting requires a canbus bypass relay block.
    Either dedicated or universal.

    Dedicated is expensive but plug n play.
    Universal needs splicing into existing wiring for the triggers but is much cheaper.

    The relays work in the same way....one main 12v feed and trigger wires from each lighting circuit plus a heavy wire from relay to lights.
    As each light is switched it activates the corresponding relay and diverts 12v to that light or lights.
     
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  11. GWAYGWAY

    GWAYGWAY Funster

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    It might be worth putting two LED bulbs in tot system as they would be about the same current
     
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  12. tonyidle

    tonyidle Funster

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    If the light works, CANBUS or no CANBUS, then the light is receiving 12v. Although I have a reasonable grasp of CANBUS I'm not sure of the detail in terms of switching. The only way the light will work but the buzzer won't is if the 12v supply is reversed. Set the vehicle with the reversing lights on then use a meter to check that the centre pin of the bulbholder is at +12v rather than at earth. If it IS at earth then the buzzer won't work and there's no simple way to make it do so.
     
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  13. Scattycat

    Scattycat Funster

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    Following on from the above comment ref positive/negative wiring.
    I've just checked via a spare 12v battery and if the the centre of the bulb is connected to the positive pole the buzzer works but if connected to the negative pole then although the light works the buzzer doesn't.
    So if I managed to re-wire the reversing light bulb holders so that the centre is positive and the outer negative would the canbus thingy see it as a fault, or, would this just give more problems that I haven't considered yet?
     
  14. pappajohn

    pappajohn Funster Life Member

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    The canbus would pobably see it as an overload.
    the filament alone will have a known resistance....add to that the buzzer and the load is increased.
    thats the reason for needing bypass relays for trailer wiring...it physically bypasses the canbus system and the canbus loads remain constant from the standard lighting.

    Get it wrong and blow the canbus will be VERY expensive....usually part of the ECU.
     
  15. Scattycat

    Scattycat Funster

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    Thanks, sounds like I'm stuffed then. LOL
     
  16. mjltigger

    mjltigger Funster

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    why not try it with some fly leads, go careful so as not to blow anything but try having the bulb separate to the holder and wire in reverse, see if it works... might save the hassle of changing it all round only for it to not work
     
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  17. pappajohn

    pappajohn Funster Life Member

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    When reversing stick yer head out the window and shout....BEEP..BEEP...BEEP.
     
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  18. pappajohn

    pappajohn Funster Life Member

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  19. hilldweller

    hilldweller Funster Life Member

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    From a legality POV I thought beepers were restricted to commercial vehicles.
     
  20. mjltigger

    mjltigger Funster

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    I have found some reference to an offence called 'reversing alarm on unauthorised vehicle' but can't track down the source
     
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