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Brake Lights Not Working/04 Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jlm11579, Sep 23, 2010.

  1. jlm11579

    jlm11579 Junior Member

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    Got pulled over in my 04 Prius yesterday because my brake lights were out (both sides according to the officer). I figured out that they were LED's and the whole tail liight assembly must be replaced to change the bulbs. What's weird is that, one of the sides will work fine, the other will be dim. or, mostly, not at all. I found some aftermarket tail asemblies ($88) much cheaper than an OEM part, however, would replacing both sides fix the problem? Or is the problem some other thing? By the way, the center lights continue to work fine.
     
  2. krg03

    krg03 Not expert, just experienced

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    If I recall there is a common ground wire. Also could be the brake switch (at the peddle). There have been other postings of the same problem. I wouldn't jump at replacing any lights or assemblies yet unless you see condensation inside the assembly. Could also just be one light messing the whole thing up. Pull one and see if it makes the other work.
     
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  3. jlm11579

    jlm11579 Junior Member

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    Thanks for the quick reply. I did eyeball the brake switch and it does seem to be engaging/disengaging properly, so i assume its OK from a mechanical standpoint. I did read something about a TSB on the possibility of oxidation in the brake switch so I called the Toyota 800#....no help from them on first try but someone is supposed to call me back within 24 hours.

    Not sure where to how to trace the brown ground wire though...

    Thanks again
     
  4. 2009Prius

    2009Prius A Wimpy DIYer

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  5. firepa63

    firepa63 Former Prius Owner

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    There was a recall for the 04 brake switch. Attached is a copy of the recall.
     

    Attached Files:

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  6. jlm11579

    jlm11579 Junior Member

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    Dealer diagnosed the problem as a short in the left-side tail light assembly. Cost of repair would be $300, including replacement of entire assembly. Paid $50 diagnostic fee but declined dealer repair. Ordered aftermarket tail assembly for $88 + shipping and will install it myself. Hopefully, the dealer was correct on the diagnosis.
     
  7. vertex

    vertex Active Member

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    Good decision and good luck!
     
  8. jlm11579

    jlm11579 Junior Member

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    BRAKE LIGHT PROBLEM RESOLVED!

    I'm happy to say the brake lights on my 2004 Prius are working again. For the benefit of those who who have experienced the same issue, I'll recap the story.

    First of all, it is important to know that the brake lights in the 2nd generation Prius are LED's contained with a sealed tail light assembly. You can't replace the bulbs alone...the entire assembly must be replaced. The owners manual makes no mention of replacing the brake lights....which tends to introduce an element of confusion to first-timers....and, to make matters worse, the parts guys at the Toyota dealers (two different dealers in my case) seem generally unaware of the brake light configuration.

    The symptoms I experienced were varied. Some times the left brake light was out, sometimes right, sometimes both. Sometimes the lights were just dim. The center light always worked correctly, however. On one post, there was mention of a brake light switch recall, however, because the center light continued to work on my car, this was eliminated as a potential diagnosis. I took it to a Toyota dealer who said the left side tail light assembly contained a short and that was causing the problem....cost to repair was roughly $300, including, as expected, complete replacement of the tail light assembly. I was quoted a cost of $230 for the OEM part from Toyota. I chose to decline the repair, paid a $50 diagnostic fee and took my car home. I ordered an aftermarket tail light assembly from carpartsdiscount.com for $88 plus shipping and just installed it this morning, using tail light removal instructions from another post at this website (thank you very much). The aftermarket part looks just like the original and it is manufactured by TYC, out of Taiwan. The whole repair took less than 30 minutes and it works fine. I did notice that the one of the LED's on the RIGHT side does not work....so I may have to replace that side at some point in the future.

    One last thing. I did have two conversations with the Toyota Customer Experience (800-331-4331). They were not able to help in any way, however they did say this: if enough people call describing the same set of symptoms, they will consider the possibility of a service bulletin or recall, if warranted. So, on any issue, whether the car has been fixed already or not, it might be a good idea to register the problem with Toyota. I was impressed by the fact that they already knew I visited the dealer and played back some of my exact words to the service rep.

    In any event, when your brake lights go out, fix it yourself for a hundred bucks, or, go to Toyota and spend triple that amount. Good luck and thanks to all for their advice!
     
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  9. 2009Prius

    2009Prius A Wimpy DIYer

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    Congrats on the restoration and one question: does the aftermarket part also use LEDs? Thanks! :)
     
  10. jlm11579

    jlm11579 Junior Member

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    Yes, the aftermarket part uses 6 LED's, just as in the factory part. No difference between the two as far as I can tell.
     
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  11. otlanof

    otlanof New Member

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    I am having the same problem with my right side or passenger side brake light not working. I ordered the after market replacement assembly. Can you send me the link that shows how to remove and install the rear tail light assembly?

    Thank U Very Much,

    Frank
    [email protected]


     
  12. Ryanpl

    Ryanpl Active Member

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    Jim, How is your replacement tail light holding up? Our light is dead and needs to be replaced.
     
  13. Britprius

    Britprius Senior Member

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    I have not removed the rear lights from my car to check, but can the lights be dismantled in the same manor as the fronts (heated in an oven) and then replace any burnt out LEDS. Must be some way to implement a cheaper repair.
     
  14. DeeTrumpet

    DeeTrumpet Junior Member

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    My right brake light failed last week. (It's six LEDs that are inaccessible until you destroy the light assembly by sawing it open.) I have a voltmeter and plenty of time, so I tested everything. The wires to the brake light first go to an electronics panel in the bottom of the assembly. (This panel is accessible, with a little coaxing.) This panel consists entirely of one diode (a current-direction control) and two groups of in-series resistors. The resistors are stamped with their ohm ratings, and you can easily see how everything connects on the printed circuit. All the resistors measured okay, as did the diode. The output voltage of this electronics panel measured about the same as the 12-volt input voltage. (I tested both the failed assembly and the good one, and got the same readings.) The LED bulbs in the bad light glowed when voltage was applied, but only at about 10% of their required brightness. I concluded that the LED bulbs must have blown, and that I had to buy a replacement light assembly. (The spouse sagely vetoed my economical idea of instead converting the white backup lights to red brake lights by changing the bulb color and repositioning one wire.)

    Removing the tail-light assembly from the car requires maybe five minutes of removing interior panels to gain access (held in place by three bolts and numerous clips), followed by one minute to unscrew two 10mm bolts that attach the light assembly to the quarter panel. Reassembly requires one minute to mount the light assembly, followed by maybe twenty minutes to work the interior panels back into position.

    Replacing the entire assembly fixed the problem, of course. I then sawed open the old light assembly with a saber saw, to look at the LEDs. I didn't cut enough to be able to see whether they are wired in parallel or in series. I pulled out one LED and applied 14 volts to it, and got the same 5% glow.

    With labor charges so high relative to parts prices, I can't really blame Toyota for designing the LEDs so we can't fix them ourselves -- very few people would do that even if the LEDs were accessible and the parts were made available. But I do miss the days when the entire job of fixing a tail light or brake light or turn signal or backup light consisted only of popping out the old bulb and popping in the new one.

    As to why the six LEDs burned out, and whether better engineering would have safeguarded them better, I can't even guess. I've read that LEDs are easily damaged by excessive voltage, and that resistors in series are therefore used to prevent a voltage surge.

    I can post clear photos of one of the LEDs and of the electronics board if anyone asks me to.
     
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  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Please post your photos.

    - What was the value of the resistors on the circuit board?

    - How many wires led from the board to the LED matrix?

    - If all six LEDs failed at one time, I would assume that they had been wired in series...

    - Did you apply 14V to one LED, without a current-limiting resistor in series with the LED? If so, I am surprised that the LED didn't burn out and open up (i.e., resulting in infinite resistance across the LED terminals.)
     
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  16. DeeTrumpet

    DeeTrumpet Junior Member

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    Patrick, good questions!

    The resistors are 6.2 ohm and 24 ohm. (Five 24-ohm resistors, R-51 through R-55. Four 6.2 ohm resistors, R-3 through R-6.)

    Two wires run from the board (CN2) to the LED array. Yellow wire is +, and black wire is -. The power to the board (CN1) is also two wires: Green wire is +, and black/white stripe wire is -.

    I too assume the six LEDs are wired in series. Doesn't this necessarily mean that if one LED blows, none will illuminate?

    Yes, I applied voltage to one LED, without a resister to limit the resulting current. I expected that 14v would burn out a functioning LED, so I started with 1.5v, then 3v, then 6v. The LED did not illuminate at all at those voltages, so I figured I could do no additional harm by applying 14v -- though I didn't expect to learn anything from doing so, since by then I figured the LED was already blown.

    Before applying any voltage, I measured the resistance across the two terminals of the one LED light, and it was infinite.

    Any opinions on the cause of the LED failure?

    I'll post nine photos separately.
     
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  17. DeeTrumpet

    DeeTrumpet Junior Member

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    Nine high-resolution photos are now posted online. Click on an image to enlarge it. Click on the image a second time to enlarge it even more.

    I'm too junior to be able to post a clickable link to the site where I posted the nine photos. They are at:

    tinyurl.com/2dzubb2
     
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  18. vertex

    vertex Active Member

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    I have also taken apart one of these assemblies. The design is poor, and not up to Toyota standards. There are two strings of 3 diodes in series. In addition, each diode is cross connected to the other in the string, so in effect, there are 3 sets in series of two diodes each in parrallel.
    So, if one diode fails, the current in the string is now only going through 1 diode and not two. This gives the remaining diode a very short life, since it is running at 2x the current.
     
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  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Thanks for providing the photos and commentary. Based upon those, I assume that the circuit consists of 120 ohms (5 x 24 ohm resistors) across CN1, plus the polarity protection diode D1 in series with 24.8 ohms (4 x 6.2 ohm resistors), leading to CN2 which allows connection to the two strings of three LED lights (per vertex). Do you agree?

    I am wondering what is the purpose of the 120 ohm load across CN1? Since there are two rear brake light assemblies in parallel, this results in a net 60 ohm load, for a current draw of ~230 mA. Perhaps this load is intended to dampen voltage spikes that might appear across CN1?

    Now let's consider the 24.8 ohms in series with the LEDs. Assume 0.7V drop across the polarity protection diode plus 1.8V for each red LED, the nominal 13.8V available would become 7.7V (since vertex says the LEDs are wired as two strings of three LEDs each).

    7.7V / 24.8 ohms = 310 mA current flow available to power the six LEDs. Since there are two strings, then 155 mA might flow through each string. Hmm, this seems like a much greater current flow than I would have expected. vertex, are you sure that the LEDs are connected as two strings of three each?

    If the six LEDs were in fact connected in series, then you would have 11.5V of voltage drop across the LEDs and polarity protection diode, leaving 2.3V. 2.3V / 24.8 ohms = 93 mA which still seems high.
     
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  20. pEEf

    pEEf Engineer - EV nut

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    They are clearly not standard 20ma LEDs, they look like the Lumileds SuperFlux units which IIRC are rated to 70ma each. That should put the total draw per side at 140ma. These kind of LEDs typically are over 2v forward, so this would affect your calculation. Until we have a datasheet, we will not know the forward voltage unless someone can check.

    Assuming 2.5v, that puts the total forward at 7.5v which seems like a good number to still safely use resistors as the current source. All 6 of them in series would be 15v which obviously cant work, so that rules out that configuration. Going any lower would mean much larger resistors as there would be much more power loss. (say assuming 3 parallel strings of 2, or worse; 6 in parallel)

    It's also very strange they bothered to use LEDs, but didn't just add some more resistors and another diode to also use them as tail lights. Many cars with LEDs use a more complex (and reliable) current source, such as a PWM controlled boost converter. The resistor-based circuit is not very reliable as any spikes can get through. There isn't any kind of regulation. I'm very surprised they didn't at least include a clamping diode of some sort to catch the spikes. Even the little LED in the glovebox has a zener!
     
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