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A-class headlamp problem

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by marksmith, Oct 15, 2012.

  1. marksmith

    marksmith New Member

    Messages:
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    Joined:
    Jun 30, 2011
    Location:
    Southampton
    Your Mercedes:
    2003 "W168" A140
    Hi folks,

    My girlfriend's W168 A-class has developed a headlamp fault. The left-hand headlamp has no main beam.

    High beam works on both left and right. Sidelights work on left and right. Main beam works only on right.

    The fuse (number "1") under the panel by the door is good, and the bulb is good. I can measure 12v at the top terminal of fuse 1 when I switch the main lights on. I cannot measure any voltage at the appropriate terminal on the bulb holder.

    Any ideas please? Are there any troublesome connectors between these two points? Or common failure points? The wiring is basically completely inaccessible in this car so I'm dreading having an awkward problem.

    Thanks!
    -Mark
     
  2. alec2

    alec2 Senior Member

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    Joined:
    Dec 11, 2006
    Location:
    East Dorset
    There is probably a relay involved somewhere.

    Easy to replace

    Alec
     
  3. area51

    area51 Senior Member

    Messages:
    353
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    Joined:
    Nov 10, 2007
    Location:
    Kent
    Your Mercedes:
    Year2000 A160
    There are no relays for lighting on the W168, all switching is done by the light switch/module.

    Possibly a light switch fault?? Or dirty/burnt contacts in the switch?
     
  4. mattkh

    mattkh Senior Member

    Messages:
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    Joined:
    Aug 2, 2006
    Location:
    England
    Your Mercedes:
    W168 1999 1.6
    Hi
    Put a new bulb on.
     
  5. OP
    marksmith

    marksmith New Member

    Messages:
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    Joined:
    Jun 30, 2011
    Location:
    Southampton
    Your Mercedes:
    2003 "W168" A140
    Thanks for the replies. As mentioned, the bulb is good - really :)

    This is very useful, thanks. I just found out that the fusebox by the door is part of the light switch, not a separate thing, by the way - useful to know.
     
  6. mattkh

    mattkh Senior Member

    Messages:
    1,573
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    Joined:
    Aug 2, 2006
    Location:
    England
    Your Mercedes:
    W168 1999 1.6
    Hi
    On your A class, is the main beam on a separate bulb, i.e. not the same bulb as the high beam, ?
     
  7. area51

    area51 Senior Member

    Messages:
    353
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    Joined:
    Nov 10, 2007
    Location:
    Kent
    Your Mercedes:
    Year2000 A160
    Personally I would change the bulb first just to be certain that it is ok.

    Then possibly remove and strip the headlight switch and clean the contact points.

    One other possibility is a damaged wiring connector on the switch.
     

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