Mystery Headlight Problem

Discussion in 'Technical' started by Jordz, Jun 6, 2011.

  1. Jordz

    Jordz Fashionably Late

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    K, so a few of the Perth guys might remember me having this problem on the Sunset Cruise and yes, it still hasnt been solved :p

    Anyways, my headlights dont work. High beams are ok, parkers are fine, just the low beam thats screwed.

    So far we checked:
    > Globes
    > Fuses
    > Relays
    > Switch has to work, or parkers wouldnt work


    So what the hell is going on?
     
  2. bigbaz

    bigbaz New Member

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    I had this in my zed, was a blown fuse, also took out a few other things in the car, possibly cigarette lighter, not 100% sure, but re check all in cabin fuses
     
  3. gibbon_tamer

    gibbon_tamer Member

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    i had same thing was a wrong type of globe in the tail lights??
     
  4. Jordz

    Jordz Fashionably Late

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    My tail lights are stock as a rock...and how would they short the headlights?
     
  5. bRACKET

    bRACKET Do Right Dean

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    I have this exact problem, started last night!
    Tell me how to fix it quick, I hate not driving at night already!
     
  6. stumagoo

    stumagoo Active Member

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    check the operation of the high low part of your switch I have seen posts where that has failed.
     
  7. bRACKET

    bRACKET Do Right Dean

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    How do I check this..?
     
  8. stumagoo

    stumagoo Active Member

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    simplest form confirm there is power getting to the lowbeam relays (pretty sure we have these right guys). Not from the main power from the battery but the signal from the light stalk. also find the plug under the dash and pack probe it with a multi meter. I am unsure of the actual wire to check (the tech section will help there), but there will be one that reads 12 volts only when low beam is selected.
     
  9. a2zed

    a2zed Guest

    Have you checked the H/Lamp Dim relay in the engine bay relay box, this is usually the main cause of this problem.
     
  10. angrybear

    angrybear Moderator

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    No, that is not how it works.

    When the headlight switch is turned on, power goes to the sockets of the high beams and the low beams - yep all four of them. The other pins on those light sockets don't go to earth, they go to the dimmer relay, which is in the fuse box near the LH headlight. The high beam pair connects to pin 87 and the low beam pair connects to pin 87a of that relay. It is the pole of that relay (pin 30) that makes the final earth connection that decides which pair (Hi or lo) of lights fire up.

    The column stalk only provides on/off power to the dimmer relay coil (pins 85 & 86). It does not power any lights.

    When the stalk is pushed forward, the dimmer relay is energised, and the normally open pin (pin 87) gets the earth. Pin 87 is connected to the high beams.

    When the stalk is pulled back, the relay coil is de-energised and the pole switches back to pin 87a, giving the earth back to the low beams and disconnecting the high beams.

    If a diagram helps, give me a whistle.
     
  11. stumagoo

    stumagoo Active Member

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    Cheers Angry bear, so the stalk earths the relays as opposed to powering them.

    Then disregard my test method, even so I have seen posts where the stalk has failed to a partial degree, the easiest way to test it then would be a cotinuity test to earth from the plug feeding the stalk.
     
  12. pexzed

    pexzed Forum Administrator

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    Yes, this is similarly how I worked out what pin to short to earth on this dimmer relay to fool the low beams to stay on with the high beams if you have HID lights.
    A similar write-up to Angrybear's is in the tech section.
     
  13. angrybear

    angrybear Moderator

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    Why don't you simply pull the Dimmer relay and replace it with a know good one. Borrow one from someone.

    It could be that this relay has failed with the pole fused to the Normally Open contact. That would give you high beam but no low beam.

    If the relay is OK, then that means the relay is energised all the time, regardless of the position of the stalk, which points to a fault in the stalk switch mechanism.

    My money's on the relay though.
     

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