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Brake lights activating other lights

  #1  
Old 09-13-2012, 09:46 PM
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Brake lights activating other lights

Last month, I changed my parking lights and license plate lights to LEDs. Today, I finally got my LED brake lights and replaced them. After changing them out, I noticed that whenever I depress my brakes, the front parking lights and the back license place lights will turn on along with the brake lights.

I've tried switching back the brake lights to the normal ones, and the other lights would go back to working normally (parking and license lights stays off when brake pedal is pressed).

Any ideas? Should I even be concerned about this problem?
 
  #2  
Old 09-13-2012, 10:11 PM
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It sounds as though you got the wrong replacement bulb for the brake lights, or didn't get it installed quite correctly. The bulbs are dual-filament bulbs, with one filament for the brake lights and one for the tail lights. The replacement LED bulbs seem to be connecting these two together, so whenever the brake lights get power, the voltage is also transferred onto the parking/tail light circuit.

With incandescent bulbs, you'd run the risk of blowing fuses due to the extra current, but that part shouldn't be a problem with the LED lights. Still, you shouldn't run like this, most especially because it would most likely also work the other way around: whenever you have your parking lights or headlights on, the brake lights will all come on as well. That's not very safe as it doesn't give the drivers behind you any idea when you're actually slowing down, besides making you look like a clueless brake-riding driver.
 
  #3  
Old 09-13-2012, 10:20 PM
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That makes sense. The LED brake lights I got are also "dual filament". They work as they should in that it turns on dimly when headlights are on, and bright when brakes are pressed. So, turning on the headlights doesn't make the brake lights fully bright. So now that the safety issue is addressed, is there a way to fix the original problem?

Thanks!
 
  #4  
Old 09-13-2012, 10:33 PM
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My GUESS is the trouble could be due to the LEDs not having as much resistance as the original filiment lamps...thereby having less of a voltage drop and passing more voltage thru to what normally is the ground side of your wiring. In many years of professional telephone systems installation and repairs, I often had troubles caused by insufficient grounding for the current flow, causing "sneak currents" when one item passed voltage thru to wiring that was not sufficiently grounded...and the voltage fed backwards thru other components.

But if this is the cause the solution isn't easy, and would involve adding more resistence into your brake light circuits. Before I would try such a Rube Goldberg approach I would instead try a different brand or value of the LED lights in your brake system. That would be the simplest way to "add more resistance" to the circuit, rather than dealing with traditional resisters and how to wire them in.
 
  #5  
Old 09-14-2012, 12:00 AM
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I bought brake lights with 27 5050 SMD LEDs, which means each SMD has 3 LEDs in it. So effectively, it should be 81 LEDs total. I think this was the highest I could find. I'll try to switch it out with a different kind/brand and see how it turns out.

Thanks for your responses!
 
  #6  
Old 09-14-2012, 12:14 AM
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by "dual filament" do u mean they are switchback bulbs?
 
  #7  
Old 09-14-2012, 06:04 AM
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Originally Posted by xxryu139x View Post
by "dual filament" do u mean they are switchback bulbs?

Your back up lights and signal lights have one purpose and therefore one circuit.

The Tail/brake light bulb serves two circuits and therefore has two filaments inside. One for each circuit.

You most likely are trying to use a bulb with only one circuit and it is trying to operate both circuits.
 
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Old 09-14-2012, 11:46 AM
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  #9  
Old 09-14-2012, 12:03 PM
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Originally Posted by kered424 View Post

A 7443 is a dual and the 7440 is a single.

Anyhow I tried putting LEDs in mine similar to you. They are shitty. Not as bright as stock. I went with some stock from Sylvania that are 20 % brighter.

I put LEd in backup and I need to change back as they are useless. Similar style to what you have but in white.
 
  #10  
Old 01-30-2014, 04:14 AM
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Hi guys - I'm having a similar problem. See https://www.fitfreak.net/forums/gene...-flashing.html

I don't remember this coinciding with the change of my brake light bulb, but I did change my bulbs recently. Maybe I should buy new bulbs and see what happens?
 
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