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Audi A4 tail light problem

Discussion in 'General Technical / How To' started by RSJ, Jul 17, 2010.

  1. RSJ
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    RSJ New Member

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    [Jul 17, 2010]
    Hi all, New Audi owner here:unsure:

    I've just bought a A4 with a fault on it's rear lights. and I was wondering if anyone knows whats going on?

    It's a 2006 model. the rear lights have bulbs in. not LED

    The car is saying theres a fault with the rear fog.

    When you turn the side lights on the rear tail lights come on dim. and also the rear fog lights up dim at the same time.

    But the rear fog still works, when you put the headlights on. and turn the rear fog on. it goes brighter.
    but the side lights stay dim.

    It seems to have 2 sidelights? one in the middle and one at the top? i don't know if thats normal?



    I've taken the rear drivers side lense out. and somones been cutting wires and joining them back up.
    but there are all connected.

    Im good with electrics. but there seems to be somthing im missing with this car. somthing isn't right.

    The earths are good.

    the sidelights arn't getting 12v's. when you give it 12v they go bright as they should be.


    What i was wonding is....
    could this be a programming thing?
    or does the car have some sort of resistor?

    If anyone can offer some sort of help, i'd be most grateful.
    I got the car cheaper because of this fault. but im starting to wish otherwise now:(

    its a diesel by the way, if that makes any diffrence
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  3. scott b
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    scott b Active Member VCDS Map User

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    [Jul 18, 2010]
    might sound daft but are the bulbs in the corect way round?

    also from memory, i know that on the newer models the side light and brake are on one wire and i think the side light and fog are one wire aswell. so it will send a lower voltage down the wire for the side light

    have you plugged the car into vagcom, what area are you in?
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  4. RSJ
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    RSJ New Member

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    [Jul 18, 2010]
    Hi, Yes the bulbs are in the right way. and there are no other bulbs off on the car.
    (as i know on other cars having a bulb off can can make other lights do diffrent thnigs)

    I havn't had it on a vagcom. but i have had it on other diagnostics.
    It did come up with something. to be honest i can't remember the code.
    It was somthing about the back lights, Might have said rear module or something on them lines.
    the fault wouldn't delete.
    To be honest. I just thought it was the car picking up a bulb off. when in fact there just isn't the right voltage at the lights.

    And yes. The Brake lights are on the top, which works on multi voltage. a 382 bulb
    But theres a side ligtht bulb right in the middle of the cluster.

    To be honest. if thats the brightness of the side lights. i know there not perfect. but it would do.

    The main thing is, the rear fog comes on too, dim of course. but it's the same brightness as the side lights.


    I was reading something the other day about resistance in the wires.
    Do the wires on the car, to the lights need to be a set length?
    Just the wires on the car have been cut and reconnected. so they would be shorter.
    Last edited: Jul 18, 2010
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  5. Watty
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    Watty ..... (_!_) Sarah's A3s #1 Fan

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    [Jul 18, 2010]
    Hi,
    If someone's previously fitted LED's or other lights, may be points to cut wires? Have you tried another board in place of yours incase there's a short across the contacts somewhere? If you try someone else's light, have a go. As you said the earth is ok, but that would be my first point to check. Mmhh, tricky one.
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  6. RSJ
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    RSJ New Member

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    [Jul 18, 2010]
    It is a tricky one..

    Its not a board though. they are bulb holders, that turn to fit in the cluster (if you understand what i mean)

    the other side hasn't been touched.

    I think someones cut them, to try and work out why it's doing it. and failed

    I've even pulled out the inner boot carpets, to check to see if the wireing has been played with, it's all as new. rear lights go off into a big loom.

    Im wonding now. if the switch could be at fault?
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