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Thread: Issues replacing 1157 bulb with LEDs

  1. #1

    Default Issues replacing 1157 bulb with LEDs

    Hi, I've replaced the 1157 taillight/brake/turn signal bulbs with red LEDs. There are 2 dual filament bulbs in each side's assembly. The issue I'm having is that when the brakes are applied, only one bulb illuminates in the assembly, the other doesn't. Both bulbs work as tail and turn just not brakes. So when the taillights are on and you apply the brakes there is not much difference in brightness, if taillights are off and you brake you only get one side of the assembly lighting up.
    The LED light only seems to go in one way so not sure if its a polarity thing (and how could it be the polarity when they still work for taillights?)
    I don't understand how one works as a brake light but not the other, and how one works as tail but not as brakes? Is that a defective bulbs, user error or something else?
    Thanks

  2. #2

    Default Re: Issues replacing 1157 bulb with LEDs

    Welcome to the board. More information is needed to answer your question helpfully, starting with some specifics: what year, make, and model of vehicle are you working on, and which exact LEDs are you trying to use?

  3. #3

    Default Re: Issues replacing 1157 bulb with LEDs

    Car is a 1976 Cadillac Fleetwood. These are the LEDS:

    https://www.аmazon.com/dp/B01KLGRIR0

    Socket/connections are identical to the old ones
    Thanks
    Last edited by Alaric Darconville; 12-01-2017 at 08:35 AM. Reason: detokenized link

  4. #4
    Moderator Alaric Darconville's Avatar
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    Default Re: Issues replacing 1157 bulb with LEDs

    Quote Originally Posted by MeToo View Post
    Car is a 1976 Cadillac Fleetwood.
    It might have some bulb outtage detection feature that the LED bulbs confuse.

    And those bulbs are complete junk.

    Try these, but you might still also need to install warning cancellers, made for CANbus systems but the theory is similar.
    "If the solar eclipse is anything like my Mitsubishi Eclipse, it'll darken the daytime sky"

    --Philip J. Fry


    (stolen from a friend)

  5. #5

    Default Re: Issues replacing 1157 bulb with LEDs

    Alaric is right. There is a giant pile of unsafe junk out there in "LED bulbs", and the ones you tried fit that description. There's more detail on this issue here. If you can return them for your money back, do so. If you can't, then throw them out and chalk it down as a lesson.

    The only two 1157 LED bulbs that will possibly work OK are these and these. Electrically either of them will work fine once you install an LED-compatible turn signal flasher, that is this kind. It has a ground wire the original flasher does not have, so you'll need to find a nearby convenient good ground to attach the new wire to. Shouldn't be difficult to find a good ground under the dash close to the flasher. The new flasher will work with LEDs, regular bulbs, or any combination. The LED bulbs to try in the back-up lights are these, and the ones to try in the front turn signals are these. Side marker lights would be these front and these rear.

    This "try" and "possibly" type of language is because you cannot just pop in an LED, say "Yep, it lights up bright and dim, so we're good", and drive off. LEDs are a basically different kind of light source than the type the lamp was designed to use, so you have to carefully check the light distribution to make sure it's safe and adequate. How to do so is described here.

    Also, be aware that if you put LEDs in the front turn signals and/or the front side marker lights, you will have to do some rewiring. The side markers are hooked up with one wire to the parking lamp feed and one wire to the turn signal feed, so that they provide two functions: a steady-burning side marker light whenever the parking/headlights are on, and a blinking turn signal repeater when the turn signal is operating. This only works if both the front turn signal bulb and the front side marker bulb are filament type; it does not work with LEDs and makes problems with feedback causing improper operation of lights all over the car. You would need to move the one side marker wire that's presently connected to the turn signal feed, so that it runs from the side marker light to ground. That will let you use LEDs without problems, but it will also delete the turn signal function of the side marker lights. If you want to keep the turn signal operation of the side markers (a very good idea especially in a large car like a '76 Fleetwood!), you would need to install the control module described at this page.

    There is no lamp-outage detection circuit on a '76 Cadillac, so you don't need warning cancellers or load resistors. Your car may be equipped with a lamp-indicator system based on fiberoptic cords transmitting some light from the lamp itself to an indicator box inside the car (or on the front fenders facing rearward so you can see them from the driver's seat). These are not affected by the type of bulb installed.

  6. #6
    Moderator Alaric Darconville's Avatar
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    Default Re: Issues replacing 1157 bulb with LEDs

    Quote Originally Posted by -Virgil- View Post
    There is no lamp-outage detection circuit on a '76 Cadillac, so you don't need warning cancellers or load resistors. Your car may be equipped with a lamp-indicator system based on fiberoptic cords transmitting some light from the lamp itself to an indicator box inside the car (or on the front fenders facing rearward so you can see them from the driver's seat).
    Interesting system. I was thinking how Toyota had the "ESP" on some models way back, and that GM might do similar things. But now that you mention the fiber-optic system, that sounds familiar.

    Regarding the 'markerflash' operation, didn't you mention some bidirectional 168 LEDs some time ago, that solved that polarity issue? Or did it have its own photometric issue? I'll have to scrape around to try to find it.

    Scraping complete:
    Quote Originally Posted by -Virgil- View Post
    The polarity question is an interesting one. I recently received some interesting LED bulbs to examine, made by this Taiwanese company. The bigger bulbs (to replace 1157, 3157, etc.) don't produce enough light, but might eventually get there. The one that made me perk up my ears was the D009 designed to replace 194, 168, W5W, etc. Not only is its light distribution surprisingly even, but it's also not polarized; it lights up equally no matter which way around the test leads are connected. I tested its function in the front side marker light of a Chevrolet with its front side markers connected between turn signal and parking lamp (as described here). With polarized LEDs, this doesn't work; you can install the bulb so the side marker function will work or flip it over in the socket so it flashes with the turn signals, but not both because this hookup depends on the bulb lighting up no matter which way current flows through it. This unpolarized LED bulb worked just like the incandescent original, no matter which way it was installed in the socket. That's a pretty neat trick, and I imagine more of tomorrow's LED retrofit bulbs will probably be designed that way.
    Last edited by Alaric Darconville; 12-01-2017 at 02:33 PM.

  7. #7

    Default Re: Issues replacing 1157 bulb with LEDs

    That was a while ago. I wound up taking out those Blick bulbs. They didn't put out near as much light as the very good Osram-Sylvania items I linked in post #5 of this thread, and trying to deal with Blick (i.e. get bulbs in hand) was a major PITA.

  8. #8

    Default Re: Issues replacing 1157 bulb with LEDs

    Thanks for the great advice, one thing I don't understand:how can an LED compatible turn signal flasher affect the performance of the light thats meant to come on with the brakes? And if the bulbs are crap, I don't get how they can work as taillights but not brakes? They are at least capable of working.

  9. #9

    Default Re: Issues replacing 1157 bulb with LEDs

    They are not capable of working. Car lights aren't like bedroom lights or porch lights; "working" means a lot more than just "they turn on and off". You were pointed at a link (third line of post #5 in this thread) explaining exactly how and why most "LED bulbs" on the market are junk, so please go read it and learn what you didn't know.

    You have all the info you need to have everything you want (LED bulbs) and need (safe car lights). Use the info or don't, that's your choice, but sitting there insisting it can't possibly be true is not a valid option.

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