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Old 09-24-2018, 06:09 PM   #1
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Default LEDs why

I have 6 volt LED tail lights (one light has 72 bulbs it’s a whole unit) At dusk tonight had the car idling outside. I noticed both taillights were lightly flickering. Doesn’t appear to be all the led bulbs but definitely some on both sides of car. Turned rt directional on and it worked as it should and left flickering went out. Did same on other side and same result. Turned headlights on and both taillights were on. Turned everything off including ignition and tail lights were dead/dark.

Why would led taillights have a light flicker’when not called for?
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Old 09-24-2018, 06:41 PM   #2
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Default Re: LEDs why

Tail light assemblies or bulbs?
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Old 09-24-2018, 06:55 PM   #3
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Default Re: LEDs why

Ok, the tail lights (some of the bulbs) were flicking with the tail lights turned off at the light switch? If that is the case, there is some voltage/current leaking into the circuit from somewhere. Could be in the turn signal switch itself. It takes very little current to light up an LED. May have already been there but you couldn't see it with a filament bulb.
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Old 09-24-2018, 06:56 PM   #4
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Default Re: LEDs why

Not a bulb. Each taillight has 72 leds. It replaces the whole unit, the red lense and the bulb.
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Old 09-24-2018, 06:59 PM   #5
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Default Re: LEDs why

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Not a bulb. Each taillight has 72 leds. It replaces the whole unit, the red lense and the bulb.
JS yes but only with truck running. I shut off and it goes out. Also note: I have it wired where turn signals work with ignition off. So I would think if voltage leak why is it not flickering with car off?
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Old 09-24-2018, 07:10 PM   #6
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Default Re: LEDs why

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It could be a bad ground but then it would affect all the LEDs. The other possibility is that the unit is defective. There may be some bad solder joints on some of the individual LEDs or in one circuit of LEDs within the unit. These can be wired in series as 6 or 7 LEDs in each circuit. In a unit of 72 LEDs there would probably be 6 circuits. If there were a bad solder joint in one circuit that could account for flickering in that one area only.

Get a unit that you know to be good and replace the flickering one. If that takes care of the problem then you know the unit is defective.
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Old 09-24-2018, 07:13 PM   #7
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Default Re: LEDs why

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It could be a bad ground but then it would affect all the LEDs. The other possibility is that the unit is defective. There may be some bad solder joints on some of the individual LEDs or in one circuit of LEDs within the unit. These can be wired in series as 6 or 7 LEDs in each circuit. In a unit of 72 LEDs there would probably be 6 circuits. If there were a bad solder joint in one circuit that could account for flickering in that one area only.

Get a unit that you know to be good and replace the flickering one. If that takes care of the problem then you know the unit is defective.
But it still has to be getting power from somewhere, a bad solder joint won't create current. The lights are flickering with the tail lights turned off (if I am understanding the issue correctly).
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Old 09-24-2018, 07:16 PM   #8
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But it still has to be getting power from somewhere, a bad solder joint won't create current. The lights are flickering with the tail lights turned off (if I am understanding the issue correctly).
Yes truck running turn signal off flicker
Turn signal on it works as designed no flicker on opp bulb
Shut truck off no flicker
Truck off turn signal on works as designed
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Old 09-24-2018, 07:27 PM   #9
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Default Re: LEDs why

I'm far from an LED expert, but that sure sounds like some type of ground loop. Just don't think you can light a diode with reverse current. But I really don't know. If you want to mess around with it you might try running a ground wire from the tail lights to the battery ground and see what happens.
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Old 09-24-2018, 07:57 PM   #10
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I'm far from an LED expert, but that sure sounds like some type of ground loop. Just don't think you can light a diode with reverse current. But I really don't know. If you want to mess around with it you might try running a ground wire from the tail lights to the battery ground and see what happens.
Nothing ventured nothing gained. I’ll try.
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Old 09-24-2018, 08:09 PM   #11
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Default Re: LEDs why

DC voltage can bleed thru a bundle of those blue crimp connectors taped tightly together, especially with a faulty ground.
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Old 09-24-2018, 09:46 PM   #12
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Default Re: LEDs why

I too have those 'unit' LED tailites in my 35 [12 volt]. I also have noticed at night, engine running, lights OFF, that the LED's slightly illuminate in time with the engine idling; rump,rump,rump.
I always assumed that because these old things give off so much electrical noise, [EMF], and the fact that LED's draw very little current, that there was sufficient 'static' to cause them to illuminate. I know a 'sparkie' [electrician] at work walked up to my idling engine with his nice flash digital meter in hand, and it blew!! [the meter]. He still whinges about that....
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Old 09-25-2018, 08:57 AM   #13
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Default Re: LEDs why

Make sure your turn signal switch where it attaches to the column is grounded. The switch body needs to have a good ground.
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Old 09-25-2018, 02:40 PM   #14
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Default Re: LEDs why

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I too have those 'unit' LED tailites in my 35 [12 volt]. I also have noticed at night, engine running, lights OFF, that the LED's slightly illuminate in time with the engine idling; rump,rump,rump.
I always assumed that because these old things give off so much electrical noise, [EMF], and the fact that LED's draw very little current, that there was sufficient 'static' to cause them to illuminate. I know a 'sparkie' [electrician] at work walked up to my idling engine with his nice flash digital meter in hand, and it blew!! [the meter]. He still whinges about that....

I think Brian might have something here. The EMF is an electro-magnetic-frequency that can affect nearby electronics. With an engine running, the spark system is creating an EMF that affects your radio as we all know. And if you look at the original poster's list of factors you will see that the EMF is possibly affecting the LEDs when the engine is running:
• Yes truck running turn signal off flicker
• Turn signal on it works as designed no flicker on opp bulb
• Shut truck off no flicker
• Truck off turn signal on works as designed

The LED (Light Emitting Diode) is very different from a light bulb. In a light bulb the current runs through a resistance wire that then glows and produces light. In the LED there is no hard connection between the + and - poles like in the light bulb. There is a gap instead like in a spark plug. Also, in an LED the charge can only go one way to bridge the gap and that is from negative toward positive. The LED is a diode and that is a one-way block for electric current. If you hook it up backwards the light will not glow.
But apparently in this case the EMF can jump the gap and cause an LED to glow intermittently.
I think.

Last edited by Cool Hand Lurker; 09-25-2018 at 07:50 PM. Reason: Put in line space.
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Old 09-25-2018, 02:48 PM   #15
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Default Re: LEDs why

Very interesting thanks for sharing that. Saves these old bones a hard trip under dash
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Old 09-25-2018, 09:27 PM   #16
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Default Re: LEDs why

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Yes truck running turn signal off flicker
Turn signal on it works as designed no flicker on opp bulb
Shut truck off no flicker
Truck off turn signal on works as designed

I'll agree with lurker. sounds like a ground.



As the vehicle runs it shakes a bit, anything from frame/fender/stands/lights are offset. Easy way to rule this out is with a frame/body to taillight temporary wire. (granted if the frame is grounded, good idea). The grounds have to make it all the way back to the rear of the car/truck through the body as designed. Fender welts/paint/rusty bolts don't help much. The negative (power) circuit in this case, is wired directly.


LEDs use far less amps. Changed my whole house out with them. *** there is LED's that are not designed for fader (rheostat) light switches and flicker as mentioned under low voltage.... But puts me back to a bad ground/full voltage available.




Maybe not factory but I like to run grounds from the body to frame then engine. A jumper wire to the rear lights off the frame. Easily unbolted, no holes added.




"I have 6 volt LED tail lights (one light has 72 bulbs it’s a whole unit) At dusk tonight had the car idling outside. I noticed both taillights were lightly flickering. Doesn’t appear to be all the led bulbs but definitely some on both sides of car. Turned rt directional on and it worked as it should and left flickering went out. Did same on other side and same result. Turned headlights on and both taillights were on. Turned everything off including ignition and tail lights were dead/dark.

Why would led taillights have a light flicker’when not called for?"


Blinkers work as a condenser (a bit) and send more volts in a jolt. Me thinks.






.

Last edited by Tinker; 09-26-2018 at 08:10 PM.
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Old 09-25-2018, 11:53 PM   #17
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Default Re: LEDs why

If you want the flicker gone install a small resistor between input and ground of the taillight.
That will eat up energy introduced in the wire from airtransmitted interference.
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Old 09-26-2018, 08:11 PM   #18
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Default Re: LEDs why

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If you want the flicker gone install a small resistor between input and ground of the taillight.
That will eat up energy introduced in the wire from airtransmitted interference.



You're joking now aren't ya.
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Old 09-26-2018, 11:26 PM   #19
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Default Re: LEDs why

No joke...resistor will keep the voltage down below the level where the leds start working.
Easy test is to hook up a normal lightbulb paralell to the ledlight and see if the flicker disapears.
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Old 09-27-2018, 12:01 AM   #20
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Default Re: LEDs why

Maybe the leds are not made for 6v then.
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