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Rear Brake Lights Dim on 2004

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by robl45, Mar 12, 2019.

  1. robl45

    robl45 Member

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    Hello,

    I notice that my rear brake lights appear to be dim on both sides and the center brake light is fine. Would both brake light modules be bad or is it more likely a bad ground or something? What is the best things to check? And if they do need to be replaced, are there any inexpensive ones that people recommend? I see a number on ebay but most get bad reviews.
     
  2. bobodaclown

    bobodaclown Member

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    Check simple things first, dusty bulbs, reseat in socket, then check ground connections. If you have a multi meter you could check the voltage at the socket. Have they ever been changed?
     
  3. sam spade 2

    sam spade 2 Senior Member

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    Most likely a bad ground. But if you don't know what a voltmeter IS.....you should take it to a shop.
    Hopefully the fix will be easy (cheap).

    One suggestion though: Test them at night when it's dark and be sure you are squarely lined up in the back and not looking at them from off to the side.

    Some of them these days don't look too bright in the daylight.

    Any chance that a previous owner had "blacked them out" ??
     
  4. robl45

    robl45 Member

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    It's the leds that are dim, no bulbs to check.
     
  5. robl45

    robl45 Member

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    I am very aware of what a voltmeter is. Where are the grounds, for this? What are the places I should check first?

     
  6. sam spade 2

    sam spade 2 Senior Member

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    LEDs are bulbs......just a different kind.

    Once you are sure that the lenses haven't been painted to make them darker, then you need to find the wires behind the lens assembly and trace them. Hopefully there will be a connector there where you can check the voltage and ground.
     
  7. robl45

    robl45 Member

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    Do we have a pinout or ground location or anything.
     
  8. bobodaclown

    bobodaclown Member

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    LEDs weren't stock on gen2. Inferior bulbs?
     
  9. robl45

    robl45 Member

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    The brakelights are LEDs I believe, they certainly cannot be changed.
     
  10. bobodaclown

    bobodaclown Member

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    Center light 3rd brake light may be, but the bulbs certainly can be accessed in the trunk behind the two panels.
     
  11. robl45

    robl45 Member

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    I don't want to argue, but there are bulbs for tail light, for reverse light and turn signal. the brake light is a row of LEDs hence the problem I'm having.
     
  12. bobodaclown

    bobodaclown Member

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    Tail light is a 2 filiment bulb. Running and brake light. Maybe you have after market tail lights.
     
  13. robl45

    robl45 Member

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    Maybe on a Gen1, but on a 2004, the top is LED.
     
  14. ChapmanF

    ChapmanF Senior Member

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    How many times will one person repost wrong information despite being repeatedly corrected?

    [​IMG]
     
  15. robl45

    robl45 Member

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    So checked tonight and the the right side was bright although only 3 of the led sections were lit bright with one lit poorly and two completely out. I plugged and unplugged the connector and got 4 lit up nicely. The left side has all but one lit up but dim and then I turned the lights on and that side lit up brightly. now I have turned the lights off and on and they are still lit up bright although the right side went back to only 3 sections lit up brightly. Either way, I have brake lights and the cop can find someone else to pull over. Still it is bothersome that this isn't the first time this has happened and clearly while the lights themselves have leds that are out, there is obviously something else wrong somwehre. Has anyone else seen this situation? I did check the ground under the rear latch which I understand is for these lights. Loosened and tightened, no difference.
     
  16. bobodaclown

    bobodaclown Member

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    Thanks for the info. Live and learn. Saw 3 bulbs.
     
  17. VFerdman

    VFerdman Senior Member

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    LEDs do go bad after a while. I have never heard of it on this car, but it's not impossible. Is there a way to pull the lights and bench test them with a known good supply?

    LEDs are NOT bulbs, they are diodes, that is semiconductors. They could not be more different than an incandescent bulb. They function as diodes, allowing the current to only flow one way and having a junction voltage drop of some kind. As they get old the junction may become damaged and the voltage drop increases and light output decreases. I would look and see what kind of LEDs they are and if there is a way to replace just the bad LEDs instead of the whole light assembly. Some soldering may be necessary, but may very well be a DIY project.
     
    #17 VFerdman, Mar 12, 2019
    Last edited: Mar 12, 2019
  18. ChapmanF

    ChapmanF Senior Member

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    There exist some posts from people who have done that.
     
  19. sam spade 2

    sam spade 2 Senior Member

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    Visit those connections again.
    But it is NOT unusual for LEDs to become intermittent for a while right before they die completely.

    Now that we know what you are dealing with, the only really good solution might be to replace the whole tail light assemblies.......because the LED strips probably are not available individually. I'm sure you won't like the price of new lens assemblies......if they are even available.
    Looks like another "good idea" that turns out not to be so good after all.

    Note: Have you noticed how many elements are "dark" in the great new LED traffic lights ??
    Almost every one of them has 10% or more gone; some a lot more.
     
  20. sam spade 2

    sam spade 2 Senior Member

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    A mostly meaningless distinction, because most are now "packaged" in a bulb-like housing so they can be replaced when necessary.

    The "engineers" made a BIG mistake with the original "non-user replaceable" designs.....when they WAY over-estimated the useful life......and/or the manufacturing quality.