Towing- brake lights

Discussion in 'Tech/Mech General' started by sdc77, Apr 5, 2014.

  1. sdc77

    sdc77 Funster

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    Hitched up a trailer and all lights worked except the brake lights... I had a look and noticed the wiring to the 7 pin plug was damaged... Replaced damaged cable but still the brake lights don't work... I have seen that the trailer wiring comes from quite far forward... But seems in good condition. Any suggestions?
    It's an 09 ducato maxi
     
  2. TheBig1

    TheBig1 Funster Life Member

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    as the van is can bus type wiring, the two options are dedicated wiring kit for the vehicle or bypass relay. you need to find out which you have fitted to work out how to fix it

    how did the wiring get damaged? if the signal wire shorted to earth, then you may have a bigger issue. assuming the wiring is now correct, either the relay is damaged or the body control module has protected the circuit by disabling it
     
  3. tonyidle

    tonyidle Funster

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    Which brake lights - van or trailer?
     
  4. sdc77

    sdc77 Funster

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    Trailer brake lights only.. Everything else works fine on both van and trailer.
    The wiring was damaged right before in entered the old 7 pin plug.... Outer sheath worn.. Rubbing against bumper bar
     
    Last edited: Apr 5, 2014
  5. tonyidle

    tonyidle Funster

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    In that case check using a spare flasher bulb that you can get it to light at the van socket (ignition on & brake pedal pressed). If you can then go to where the trailer wire connects at the rear of the trailer & test there.

    Alternatively you could first check that the earth connection at the trailer lights hasn't failed. Switch the van lights on with one flasher going as well. Check that the flasher doesn't dramatically affect the trailer tail lights & that it flashes at full brightness. Then apply the brakes & note any dramatic change in tail lights or flasher. If anything illogical happens to the trailer lights check the earth connection to them (white wire).
     
  6. TheBig1

    TheBig1 Funster Life Member

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    after repairing the wiring, if the brake light feed still wont power up, you could try resetting the bcm by disconnecting the battery for 15 minutes. if its a bypass relay blown though by shorting an output, it will need to be replaced
     
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