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Warning light on dash

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by redspudder, Dec 22, 2008.

  1. redspudder
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    redspudder Sparky

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    [Dec 22, 2008]
    I have today got a problem with the orange warning light on the dash showing i have a light out and writing in the red part saying "front dipped beam right "this came on once or twice last week and went away today it was on when i went to work and stayed on when i returned home and is still on now when i start the car the only problem is that i dont have a light out have checked all of them and had a quick look at the wiring and all seems to be fine any ideas what it could be maybe a sensor?I have rang a local specialist and told me he can do a diagnostic check for £35 to try and find the fault
    #1
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  3. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Dec 22, 2008]
    Do you have HID's fitted?
    #2
  4. J7USS
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    J7USS Shuddup Foooool!!

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    [Dec 22, 2008]
    Im getting this same fault too :uhm:but mine goes away when I adjust the level up and down!!

    I have Hids too.
    #3
  5. redspudder
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    redspudder Sparky

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    [Dec 22, 2008]
    No but i have have changed the lampsbut that was in August
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  6. J7USS
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    J7USS Shuddup Foooool!!

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    [Dec 22, 2008]
    have you tried giving it a knock on the headlight and flick the level switch up and down few times!!
    #5
  7. redspudder
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    redspudder Sparky

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    [Dec 22, 2008]
    Ive just been out in the car and the fault is no longer there?this is confusing,i rang 2 places today one said it could be a number of things and could do a diagnostic check the other said it sounds like it could be the dashboard and that would be very costly i am prepared to run with it for now as it seems to be intemitent fault but is confusing me i am a sparky by trade and have done most checks on the light and cant find anything obvious wrong electrically although car electrics are different to what i usually work with but have tried things that i would normally and all seems sound
    :uhm:
    #6
  8. evilscotsman
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    evilscotsman Space Cowboy

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    [Dec 23, 2008]
    the ecu has to be measuring the current through the lamp mate, since the warnings only show when the lamps are operated - so that rules out impedance testing. There can't be some kind of inductive coil pickup like we use on motors for stand-still current detection because its DC - I reckon the current down the wire is measured at source.

    That points to a fault at the convenience & lighting unit since the detection is likely done at the supply point, not at the endpoint of the circuit. The lamp could form the 4th leg of a Wheatstone bridge (in the ecu), the other 3 resistors are of known value and so the lamp current can be calculated from the total current in the circuit using the K-Law.

    If one leg of the bridge was open circuit, the lamp would still receive current to operate properly, but the bridge current would be wrong and trigger a warning.
    #7

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