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Headlight (low beam) Issue

Discussion in 'Gen 2 Prius Main Forum' started by Ruming, May 3, 2022.

  1. Ruming

    Ruming Junior Member

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    2004, halogen lights, Canada with DRL

    A few months ago, right bulb low beam filament burnt. Replaced both with LED. It's been working fine, except the low beam stays on during daytime as DRL.

    Last night, noticed both low beam not working (not out, but very dim), drove back with high beam.

    Changed back to halogen bulbs:
    LEFT: High/Low beam working, DRL working.
    RIGHT: Low beam filament burnt instantly. High beam working.

    Low beam fuses are good. Relays clicking.

    Where to look into? Thanks
     
    #1 Ruming, May 3, 2022
    Last edited: May 3, 2022
  2. Another

    Another Senior Member

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    Maybe contact the manufacturer of the LEDs your using
     
    #2 Another, May 3, 2022
  3. Ruming

    Ruming Junior Member

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    They are not out, just very dim, so I guess something in controlling circuit is wrong, not LEDs (unlikely to fail both sides same time)
     
    #3 Ruming, May 3, 2022
  4. Another

    Another Senior Member

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    There are electronics in the led module
    Both have same number of hours use so may be a MTBF problem
     
    #4 Another, May 3, 2022
  5. pasadena_commut

    pasadena_commut Senior Member

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    Odds of both failing randomly on the same day, given MTBF value which is probably ~5000 hours, is very small. However, both could easily fail on the same day due to a common adverse event, like a voltage spike or a wiring problem. I would check the LEDs outside the car to see if they light up when hooked directly (in the proper polarization) to a 12V source. If they still work they are not the problem, something in the car is. So put the LEDs back in and measure the voltage on both sides of the connector. If it isn't very close to 12V and ground, then there is an issue with the car. Note that dim headlights are often the result of a bad ground.
     
    #5 pasadena_commut, May 3, 2022
  6. Ruming

    Ruming Junior Member

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    You are correct. I changed left to halogen, it's working. Thanks
     
    #6 Ruming, May 3, 2022
  7. Ruming

    Ruming Junior Member

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    Both LED light up on the car, just dim on low beam. Moved back to halogen, looks good now. Will report back if they go wrong in a few days. Thanks for the reply.
     
    #7 Ruming, May 3, 2022
  8. Another

    Another Senior Member

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    I’d see if they are still under warranty with the vendor.
    Some LEDs not necessarily for cars are not made well in my experience
     
    #8 Another, May 3, 2022
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