LEDs why

[30-9]

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?

[51 MERC-CT]

Tail light assemblies or bulbs?

[JSeery]

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.

[30-9]

Not a bulb. Each taillight has 72 leds. It replaces the whole unit, the red lense and the bulb.

[30-9]

Originally Posted by 30-9

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?

[Cool Hand Lurker]

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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.

[JSeery]

Originally Posted by Cool Hand Lurker

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).

[30-9]

Originally Posted by JSeery

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

[JSeery]

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.

[30-9]

Originally Posted by JSeery

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.

[cmbrucew]

DC voltage can bleed thru a bundle of those blue crimp connectors taped tightly together, especially with a faulty ground.
Bruce

[Brian]

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....

[TJ]

Make sure your turn signal switch where it attaches to the column is grounded. The switch body needs to have a good ground.

[Cool Hand Lurker]

Originally Posted by Brian

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.

[30-9]

Very interesting thanks for sharing that. Saves these old bones a hard trip under dash

[Tinker]

Originally Posted by 30-9

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.






.

[flatheadmurre]

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.

[Tinker]

Originally Posted by flatheadmurre

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.

[flatheadmurre]

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.

[Tinker]

Maybe the leds are not made for 6v then.

[dumb person]

OK so i didn't read the whole thread but i noticed LED lights will flicker when turned off if the engine is running. It appears to be interference from the ignition circuit but without replacing the ignition source i can't say for certain. Kind of like how if you hold a neon light tube near an ignition wire & see it glow.

[Cave]

RFI?
I think Brian was the first to suspect an EMF. I'm no electrician, but I recently held an LED flashlight near the carb and voila, it started blinking. The closer I moved it to the distributor the more the flashing effect. I'd almost guarantee it was Radio Frequency Interference from the plug wires. I already have the "modern" dist. cap (0n my 31 "A"), I think I'll try sprial wound plug wires and see if there is any change.

[fordor41]

leds will operate on a range of voltages. If the voltage is low you've reached the thresh hold of their operation and they can flicker. I found that out when I installed LEDs in my dash and they were too bright so I added a pot to tone them down. If I went too low they would flicker or go out. Maybe you're getting correct voltage to the LEDs with motor off and a voltage drop when running or LEDs are not for 6V operation. Pull one out and hook it up to the battery. If it operates OK then I suspect low voltage

[Red98]

The tail light LEDs contain both semiconductors which produce light. And they contain semiconductors which control the voltage and current sent to the LED chips. It's those control chips which pick up EMI radio waves from the ignition altering their output to the LED chips. You will also find your tail lights produce EMI which cause interferrence with weak AM radio stations when you press the brake pedal sending voltage to them. PLUS we know where they were made don't we. Place an electrolytic capacitor across the tail light wires. A series inductor would help but you don't have one.

[revkev6]

Originally Posted by flatheadmurre

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.

isn't a capacitor the generally accepted component for this use??

[Jack E/NJ]

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My tooth amalgams used to tingle when I got too close to packard 440 or a clear channel AM radio station. Might've heard music from them too. Jack E/NJ

[Cave]

Cave back again - The '31 A with "modern" dist. cap, as mentioned above caused the LED flashlight and LED dropcord lamp in my garage to flicker if I put them near the dist. Today I made up a set of spiral wound coil and plug wires (from a cut-as-needed kit) and there is NO RFI at all, and the old gal purrs just like she did with the steelies. YMMV but thought I'd pass it on for what it's worth... Safe motoring.

[Ggmac]

Emf. Just watch what it does to a digital volt meter . My guess

[Brian]

'Emf. Just watch what it does to a digital volt meter . My guess'

Absolutely...as in post 12

[flatheadmurre]

Originally Posted by revkev6

isn't a capacitor the generally accepted component for this use??

Capacitors are commonly used to keep voltage spikes from contact points and brushes down.

My take on the led flicker was that anything that would bleed away the voltage buildup would work so a small resistive load was the cheapest smallest solution that came to mind.

May be that the circuit has a regulator in it and if it´s truely airtransmitted EMI the only way to fix it is adressing the source...or changing to a different driver of the leds...