LED Tail lights

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bgrencik

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My truck has aftermarket LED taillights on it. When I use my turn signals they blink fast as if a bulb is out. I had it checked out and they said it’s because the LEDs are drawing too much power since they aren’t halogen, like the original oem lights. They told me the only way to fix this is to go back to halogen taillights. Is this true or can I install something to prevent this? Thanks
 

TatertotScott

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The reason for the fast blink is likely the LEDs, but the explanation is incorrect.

It draws LESS power, thereby leaving more for the heated spring in the blinker relay to heat faster, cause it to oscillate faster.

Solutions include: get bulbs with resistors, get an electronic flasher, switch back to incandescent (not halogen), or put a resistor in line.

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bgrencik

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Thanks for the response! And yes less power. That was my bad. Same with halogen vs incandescent. Had a brain fart. What would be the easiest solution? I don’t want to replace with incandescent since I love the leds. Will any resistor work?
 

TatertotScott

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Thanks for the response! And yes less power. That was my bad. Same with halogen vs incandescent. Had a brain fart. What would be the easiest solution? I don’t want to replace with incandescent since I love the leds. Will any resistor work?
I actually have never added a resistor personally, but they are available at many auto retailers

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MADDOG

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Which resistor to get depends on how many LED bulbs are in your tail lights.

However, as a rule of thumb, a 6 ohm/50 watt inline resistor should do the trick.

Here's a link to what I am referring to from a company I've used many times in the past:

https://www.superbrightleds.com/mor...BoQdy0-FhkL_mzTFe-LOkdgJdeOYB7BRoCKKMQAvD_BwE

Here's a great video from Diode Dynamics on how to install resistors:


The process is similar for a tail light assembly, you just add the resistor into the tail light pigtail that goes to the truck's wiring harness & connector.
 

Big Blue Hemi

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So this is a typical problem with led taillights?
Was going to go to LED but not if I'm going to run into issues. Glad I saw this thread. You would think that the manufacturer would want to produce a product that works correctly.
 

Wahrsuul

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Yes, and I don't understand what Dodge was thinking. The flashers are controlled by one of the "computers" in the truck, and yet they're still affected by the draw of the bulbs? You's think it would be a solid state flasher and wouldn't be affected by that.

Many of the LED tails I've looked at already have the resistors built in. Just ask the seller. If they're not sure, I'd pass.
 

indept

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Which resistor to get depends on how many LED bulbs are in your tail lights.

However, as a rule of thumb, a 6 ohm/50 watt inline resistor should do the trick.

Here's a link to what I am referring to from a company I've used many times in the past:

https://www.superbrightleds.com/mor...BoQdy0-FhkL_mzTFe-LOkdgJdeOYB7BRoCKKMQAvD_BwE

Here's a great video from Diode Dynamics on how to install resistors:


The process is similar for a tail light assembly, you just add the resistor into the tail light pigtail that goes to the truck's wiring harness & connector.

Not inline ( which would imply series circuit), you put the resistor in parallel.
 

TatertotScott

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Not inline ( which would imply series circuit), you put the resistor in parallel.
Are you sure? Won't electricity take the path of least resistance and "bypass" the resistor?

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indept

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Are you sure? Won't electricity take the path of least resistance and "bypass" the resistor?

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I'm sure. It will just add to the led current which is what you want. If you put it in series it will reduce current even more. Just make sure there is ventalation around the resistor. It will dissipate over 24 watts so it will get hot.
 

TatertotScott

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I'm sure. It will just add to the led current which is what you want. If you put it in series it will reduce current even more. Just make sure there is ventalation around the resistor. It will dissipate over 24 watts so it will get hot.
Ok. I am no expert, just wondering. Thanks.

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MADDOG

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"inline" was a poor choice of descriptive term. Wiring a resistor, with a metal lead at both ends, is done in parallel. The resistor leads wire to both sides of the power circuit.

F0I9J52HVF70J74.LARGE.jpg
 

indept

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I measured current for both led & incandescent. The incandescent (hallogen) 3157 was about 0.5a for the parking lamp filament and 2.2a for the stop / turn signal filament. The led I have was 0.13a for parking & 0.6a for stop / turn. And the led was WAY brighter. This was done at 13.5v which is the low end of average alternator output.
 

indept

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I was under the impression that the lighting voltages could be adjusted with programming in the BCM. There is a thread on here titled AlphaOBD

https://www.ramforum.com/threads/alfaobd.123982/
I did get that. The only selection I found on my '17 was for each bulb there was a section for LED bulb where there was a pulldown menu with either LED or No as the choices. I selected LED for all of my bulbs and the truck is now all led with no issues.
 

Mcgruff

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"inline" was a poor choice of descriptive term. Wiring a resistor, with a metal lead at both ends, is done in parallel. The resistor leads wire to both sides of the power circuit.

F0I9J52HVF70J74.LARGE.jpg

This is correct. Resistors in series (in line) are additive (r=r1+r2+r3). Resisters in parallel are inverse additive (1/r=1/r1+1/r2+1/r3). Meaning adding a resistor in line will increase resistance and thus decrease current draw (more obsitcles in the way of electricity flow). Adding in parallel will decrease resistance and thus increase current draw (more paths for electricity to take). An incandescent has very little resistance and draws many amps. When there is too much resistance (such as using LEDs) there is too little current flow (too few amps) and truck assumes bulb is out. By adding an extra resistor in parallel you lower resistance and increase current (amps) enough to not trigger the warning.
 

JB1

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I did get that. The only selection I found on my '17 was for each bulb there was a section for LED bulb where there was a pulldown menu with either LED or No as the choices. I selected LED for all of my bulbs and the truck is now all led with no issues.

Excellent, so now if you have LED bulb in your fogs it won’t cause a bulb out message?

My OBDMX gets delivered tomorrow so I’m gonna have to play catch up with you guys
 
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