How to Install Load Resistors for LED Turn Signal Lights

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About: Everything about automotive LED lights

Why are installing load resistors necessary for LED turn signal lights? If you don't install load resistors (also known as equalizers) with LED turn signal bulbs, you will experience the notorious hyper flash issue. Hyper flash is exactly what it sounds like, where the turn signal light flashes rapidly and is almost headache inducing. Not only is this ugly, but you may also attract the police who think your bulb is burned out. This sounds completely unnecessary and a huge hassle to boot.

You will need 50W 6 OHM load resistors and tap the load resistor to the stock harness in parallel. Load resistors also have no negative or positive, making it easier for you because you wouldn't have to worry about which wires goes to which side.

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Step 1:

1156, 3156, 7440 are single filament applications so there are only two wires (one positive, one negative). This is very straightforward as you need to simply tap the load resistor wires between the two wires.

Step 2:

1157, 3157, and 7443 are double filament applications which have three wires (one shared negative, one positive dim mode, and one positive brighter/blinker mode.) There is a little more trial and error involved with the wiring. We recommend you tap the load resistor between the most vivid wire color (usually the brighter/blinker) and the least wire color (usually negative). In this tutorial, we are going to try to tap the resistor the red and black wires.

Step 3:

Test the turn after the wires are tapped. If the turn signal still hyper flashes, take the wires out and tap it to another wire and try again. The most times you will try to tap the wires is three times. We are going to assign each wire with a letter for easier reference: Red-A, Green-B, and Black-C. We originally tried A and C and tested it to see if it works. If not, try and C. If that still doesn't work, try A and B.

Step 4:

If you have tried all three ways and the hyper flash issue is still there, then perhaps the issue causing this is the connection. Many people install load resistors with a T-tap because it sounds easy, but we definitely don't recommend this route. T-taps are sometimes unable to cut through wire and causes a loose connection or intermittent function. We recommend you directly merge the load resistor to the stock harness. Actually, my professional stereo installations have installers merge the wires instead of using T-taps.

Step 5:

How to merge the wires: We recommend you use a wire stripper to expose the copper wire in a small slit without damaging anything. If you don't have a wire stripper, you can also scrape through the plastic using a knife or scissors. Don't forget to use electrical tape to cover it after you connect the wires. An awesome thing about merging wires is that they have a 100% success rate every time. You won't have that intermittent working/not working issue like the T-taps. Don't forget to mount the load resistor to the metal using zip-ties and not double-tape.

Step 6:

Summary:

1. Merge wire instead of using T-taps for a perfect connection.

2. Always try different wire combinations for double-filament bulbs.

3. Mount the resistor to metal so you can prevent heat damage.

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    106 Discussions

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    WParrav

    Question 7 weeks ago

    Here is a good one. I have installed led brake/turn/tail lights and resistors on my 2012 F-150. Everything works fine (no hyperflash). However, if I have my marker lights on and activate my turn signal, the signals hyperflash. Turn off the lights and the go back to normal. How do I correct that?

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    Wo1fMane

    1 year ago

    OEM flashers work by sensing the current draw, and if the current draw is much less than the factory setup it assumes that a bulb is out and flashes very rapidly in order to alert the driver that a bulb is out. LEDs draw a lot less current (and therefore power) than the equivalent incandescent bulbs, so the OEM flashers don't recognise them and act as if a bulb is out. Load resistors work by deliberately wasting power by converting it directly to heat rather than light. If that sounds dumb, it is. Load resistors should be your very last resort if you can't find a replacement LED flasher that will work with your vehicle. A replacement flasher has the added benefit of being plug-and-play, requiring no modification whatsoever to your vehicle or its wiring.

    Don't use a 50 watt resistor just because some guy on the Internet tells you to. It's overkill and wastes power, not to mention creating a lot more heat than necessary in many situations. Look in your vehicle's owner's manual (or on the existing incandescent bulb if it's readable) and use the wattage of the existing lamps or maybe even slightly less.

    Also, if you're doing a permanent install never just "merge" the wires as described above. They will corrode, even if you cover them with electrical tape, and eventually the connection will degrade. Always solder the wires.

    I have two motorcycles; one is 100% electric and the other is an ICE bike that is known to have a weak electrical system.

    I have converted the electric bike to all LEDs in order to save energy and maximize range. I replaced the flasher on it and it works like a charm.

    Unfortunately, the ICE bike for some reason doesn't work with the flasher that according to the schematics and pinout should work. Using load resistors completely defeats the purpose of using LEDs because it just uses the same (or in the case of a 50 watt resistor, WAY MORE!!!!!) power than the original bulbs. However, I did find that 6 watt resistors work (as opposed to the original 10 watt bulbs) and still save a couple of watts over stock. Not ideal, but it works as a stop-gap until I can figure out why the flasher replacement doesn't work.

    12 replies
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    ShaneB112Wo1fMane

    Reply 1 year ago

    Wo1fMane, you've misunderstood how resistors work. The wattage rating of a resistor is the maximum power the resistor is rated to dissipate, before possibly overheating or failing. If you choose a smaller wattage resistor, but still the same ohm resistance, you will be overloading the resistor, and it will likely overheat and fail. Maybe not immediately, it heavily depends on the overload severity, ambient temperature, duty cycle, etc... There is a simple calculator available online to determine what wattage resistor is required for a given voltage.

    Using this calculator, enter the voltage of an operating car ~ 14V, and the ohms of the chosen resistor - 6, and press calculate. You will see that this resistor will be dissipating 32.666 watts, and the 50 watt resistor used in this instructable is absolutely warranted.

    Your 6 watt resistors will STILL BE DISSIPATING 32.666 WATTS, and they are grossly under-rated for the application and will likely eventually fail. The only saving grace you have, is that during a turn-signal operation, they are only on about half the time, which will dramatically reduce the heat dissipation required by each. If we call the duty cycle 50%, then you are effectively dissipating 16.333 watts worth of heat through them, if averaged over time. This fact, coupled with the fact that turn signals tend to be operated in short bursts, is likely why your 6 watt resistors are still working... so far.

    Try leaving them on for a few minutes and see how hot the resistors get... Please have a fire extinguisher ready.

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    Wo1fManeShaneB112

    Reply 3 months ago

    You've misunderstand how cars work. No turn signal bulb is anywhere near 50 watts. That's headlight territory. According to your calculations, the resistor will be dissipating more power than the original bulb. Also, my resistor is 6 Watts, not 6 Ohms. I never said how many Ohms my resistor was. Those other resistors need to be 50 Watts because they have too little resistance. You need rethink your approach.

    By the way, my "insufficient" resistors are still working fine more than a year later. But that's only because I haven't had the spare time to track down why the flashers I've tried to use don't work in spite of the pinout being correct according to the wiring diagram and the markings on the OEM flasher. Sooner or later, the resistors won't be necessary.

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    Wo1fManeShaneB112

    Reply 1 year ago

    There are too many problems with your calculations to list. But a glaring problem is that the resistors' values aren't actually given. Using that calculator, the 6 Watt resistor would have to be 32 Ohms, and the 50 Watt resistor would have to be 4 Ohms. But that ignores the rest of the circuit and that calculator only works for a single component. If you put a 4 Ohm resistor in series with the LEDs, and assuming the LED lamp draws a generous 1 Amp, you get a power dissipation of only 4 Watts and a voltage drop of 4 Volts across the resistor, which leaves 10 Volts for the LEDs. That's well within the operating specs of everything.

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    Wo1fManeWo1fMane

    Reply 3 months ago

    See above. The point is that the whole point of those resistors is to draw enough power to "fool" the flasher into thinking you're using an incandescent bulb. So yeah, they're drawing a significantly large percentage of their rated power, and defeating the major purpose of LED lights, which is to save power and not throw off a bunch of waste heat.

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    Wo1fManeShaneB112

    Reply 1 year ago

    Wiring the resistor in parallel (which is the only way your calculation makes sense) is a huge waste of power and actually increases the load on your electrical system over stock incandescent bulbs, which is really dumb and lazy. If the LEDs can't function with the resistor in series, then they are poorly designed and made and you shouldn't be using them.

    The right way to fix the problem is to replace the flasher with one that flashes at the same rate regardless of the load, so it works with both LEDs and incandescent lamps in any combination. It saves energy and requires no modifications to your vehicle at all. Plug and play. Most people who don't properly inspect their own vehicles for proper function of basic equipment like lights don't know or care what that fast flashing means anyway.

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    Wo1fManeWo1fMane

    Reply 1 year ago

    P.S. Your headlight bulbs are 55 or 60 watts. If you use a 50 watt resistor you're turning the same amount of energy directly into heat that your headlights turn into light. And have you ever touched a lit headlight bulb? (DON'T!!!) They already waste a lot of energy as heat. With sealed beams they're just hot, but with halogens you'll instantly get burned. (You don't want to directly touch halogen bulbs even when they are cold because the oil from your fingers will make the bulb break when it heats up. Use gloves or a clean rag to handle and install them.)

    Don't use 50 watt resistors unless it's specifically called for in your application.

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    gilligan8Wo1fMane

    Reply 3 months ago

    But the wattage of your bulb is how much power it will DRAW.

    The wattage of a resistor is how much power it can handle.

    These are VERY different.

    The OHM is what determines how much power the resistor will "see" through it. No matter what wattage resistor you have, it will see the same power. If it's underrated then it will burn up.

    Put a 1/4 watt 6 ohm resistor across your battery and watch it burn up in smoke. This is why you need a larger wattage resistor to handle the power that will go through it based on the resistance.

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    Wo1fManegilligan8

    Reply 3 months ago

    You're wrong, and completely missing the point. The point is that you need those high power resistors BECAUSE THEY ARE GOING TO DRAW A LOT OF POWER. If a small resistor would do, then you're drawing a small amount of power and it's no big deal. But the fact is, you HAVE to use those big resistors because they WILL draw nearly that much power, and then dissipate it as heat. It is hugely wasteful (and sometimes dangerous, because those resistors can get VERY hot) and defeats most of the benefit of using LED lamps.

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    gilligan8Wo1fMane

    Reply 3 months ago

    But wait, then how am I wrong? That's exactly what I am saying.

    You NEED the high power resistor because the circuit will draw a lot of power (it's Ohms Law).

    yes, it's wasteful and it produces a fair amount of heat... and maybe it's the the best way to "fix this"... but it's not incorrect.

    For your E-Bike it's a terrible plan because like you said, it's wasteful. For an ICE then it doesn't really matter that much.

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    Wo1fManegilligan8

    Reply 3 months ago

    You're still wrong. All bikes have a relatively tiny "alternator" and will benefit from power savings, especially if you start adding accessories like auxiliary lights, heated grips or phone chargers. A lot of ICE bikes have problematic electrical systems from the factory, and every little bit helps. Conversely, adding more current draw back in with load resistors is a bad idea.

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    gilligan8Wo1fMane

    Reply 3 months ago

    You seem to like to tell people they are wrong a lot.

    This instructables was started about cars. You brought your bike into the fray.

    Either way, Ohms Law is Ohms Law... I don't know why you are so determined to be right and someone else be wrong.

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    Wo1fManegilligan8

    Reply 3 months ago

    There's the pot calling the kettle black. I made a comment, and you are the one who said I was wrong. I'm just giving examples why that's not the case. As for bike vs. car, it's just a handy example. I also have a car that has the flasher circuit built into the ECU, which means there's no possibility of replacing the flasher. I still want to use LEDs, but I am *NOT* going to use load resistors, because for all the facts I keep repeating it's a dumb idea. I will find another way that doesn't waste power or risk fire.

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    ArturoG67

    Question 1 year ago

    Hi, I want to intall this resistor for a motorcycle led headlight, because "Ligth Out" signal is prompted. How many resistor do i need? Is a BMW R NINET Scrambler with H4 connector. Regards.

    1 answer
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    Wo1fManeArturoG67

    Answer 3 months ago

    Using load resistors on headlights is a very bad idea because they are always on and draw a lot of current/power and you will be creating a major fire hazard.

    Look for "CAN bus compatible" bulbs, disconnect the instrument panel bulb (or just cover it with opaque tape), or stick with OEM bulbs. Never use load resistors on headlights.

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    RobertC631

    Question 1 year ago on Introduction

    I have a 2007 base (V-6) Mustang with 6 brake light panels with bulbs. Are changing to LED bulbs going to initiate the "hyper flash" and require the load resistors ? Thank you.

    2 answers
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    Wo1fManeRobertC631

    Answer 3 months ago

    Pretty much all vehicles have this issue, because it is deliberately designed in. Even newer vehicles that have factory electronic flashers rather than bimetallic strip flashers are designed to work this way. If you can't replace the flasher you're better off just sticking with incandescent bulbs.

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    ab1jx

    11 months ago

    Usage of the term "load resistor" in this context made me cringe. A load resistor is something you might use when testing a power supply to simulate a load, or on an audio amplifier you just repaired and you want to do a "burn in" test by cranking it at full volume overnight into a dummy load without making any noise to test it.

    This is a current limiting resistor https://en.wikipedia.org/wiki/Current_limiting and you use Ohm's law or an online calculator to figure the value. There are a slew of them, look at https://duckduckgo.com/?q=%22current+limiting%22+r...

    If you want to run a single cheapo LED from 12 volts you probably want a maximum current of 20 mA or 0.02 amps. This calculator http://ledcalc.com/ says you want a 470 ohm resistor and it needs to be at least a 1/4 watt resistor. Better to use 1/2 watt, heating resistors usually changes their value over time.