LED Brake Lights - FFCars.com : Factory Five Racing Discussion Forum
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post #1 of 8 (permalink) Old 07-09-2019, 03:03 AM Thread Starter
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LED Brake Lights

With the headlights on, I don't get a noticeable difference in tail light output when I hit the brakes. (LED Bulbs )

I have load resistors installed at each bulb. If I take out either LED and replace it with incandescent, the remaining LED works as it should.

Headlights off, brake lights work as they should.

Any ideas??


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post #2 of 8 (permalink) Old 07-09-2019, 03:20 AM
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Headlights and brake lights are on totally separate circuits. Interaction between the two doesn't exactly make sense. The running lights, however, turned on by the headlight switch, are one of the two elements in your tail lights. Check the wiring in your lights. And make sure the LED bulbs are keying properly into the socket. Same as the regular incandescent bulbs. It's easy to get them in wrong. If you have the lights wired normally without any additions, e.g. relays, trailer modules, etc., all four low intensity elements should light with the running lights, one high on each side for the brake lights, one high on each side for the turn signals/hazards.

Also, the single purpose of load resistors is for turn signals. So that shouldn't be in play here. LED bulbs typically don't have enough current draw to trigger the traditional thermal style flashers in your fuse panel. I'd highly recommend pitching the load resistors and just change your flashers (turn signal and hazards) to solid state flashers. Widely available on-line or at most part stores. They will run either LED's or incandescent and typically last much longer. Aside from the unnecessary complication, load resistors negate the low current draw advantage of LED's.

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post #3 of 8 (permalink) Old 07-09-2019, 04:57 PM
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The link you supply for the LEDs from Amazon were the white ones and should only be used for back up lights. Please let us know if you are using the red LEDs for the rear lights and the yellow ones for the fronts. I am only asking because LEDs produce a very small spectrum of light and color filters do not work with them.
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post #4 of 8 (permalink) Old 07-09-2019, 09:31 PM
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colored filters

Brastic is correct in saying that colored filters don't work well . . . if at all.

Just for conversation sake, let's say that a WHITE LED lamp puts out 100% light in 25% segments of the four basic colors (blue, green, yellow and red), all colors mixed together produce white light.

IF you put a white LED under a red filter, only the red segment (25%) will get out past the filter . . . making the lamp seem dim.

IF you put a red LED under a red filter, all 100% will get out as red is the only color the LED is producing.

Same goes for the other colored LED's available.

So, to get the best light output from your LED's, get them the color of your lenses.

Clear as mud, right?

And, the electronic flashers are the best way to go, as was mentioned by Paul above . . . no need for ballast (load) resistors.

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post #5 of 8 (permalink) Old 07-09-2019, 10:01 PM
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If everything is correctly wired and you still are not getting enough change for your liking then you can just add resistors to the tail light lead until it dims sufficiently. I do this all the time in order to make a standard LED tail light into a running/brake light. I have a nice little box where I can vary the resistor values while the LED is attached and see what resistance is required. Then go and buy the right resistor and put it in line on the tail light line. Easy peasy.


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post #6 of 8 (permalink) Old 07-12-2019, 03:22 PM
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I have been thinking about your circuit and I think that I have an idea for you to check. The rear lights are the old 1157 type with two light outputs. A normal for running lights and a bight for stop or turn. You said that you installed a resistor. Did you install the resistor on the ground side or one of the positive side? My guess is that you have it on one of the positive sides. Personally, I do not like putting load resistors in cars. I just spend the $10 and get a new blinker.
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post #7 of 8 (permalink) Old 07-12-2019, 10:33 PM
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Left the standard bulbs in the front turn signals & did not need any resistors for the rear lights


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post #8 of 8 (permalink) Old 07-13-2019, 05:58 PM Thread Starter
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Working

Got it working!

I had misspoke about the load resisters, they were only on the blinker circuit, one one each side in the front. (Oops)

Spent all day checking the wiring, and voltages and every combination under the sun. Removed the load resisters from the font, changed the blinkers out from the blinker circuit to LED polarity independent blinkers. Moved on to the brake circuit, still couldn't find a problem, the bulbs were installed correctly, I couldn't get them to go in the wrong way (hammer?).

The following symptoms remained (headlight function is referenced only because of taillight function):

2 Incandescent, headlights off: work as designed on/off
2 led, headlights off: work as designed, on/off
2 Incandescent, headlights on: work as designed, tail lights up, gets brighter when brake is depressed
2 LED, headlights on: tail lights up, no change when brake is depressed
1 Incandescent, 1 LED, headlights on: work as designed, tail lights up, gets brighter when brake is depressed, repeats with LED/Incandescent on either side

Switched to another brand of LED, and everything works fine.

Thanks for the tip on the red LEDs. I read up on it a bit, and it seems that you are correct. I will grab the correct colors next.

Thanks again for all the help guys.

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Last edited by FFR9375; 07-13-2019 at 06:02 PM. Reason: oops
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