How to Install Load Resistors for LED Turn Signal Lights

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Introduction: How to Install Load Resistors for LED Turn Signal Lights

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.

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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    75 Discussions

    Not a particularly useful instructable. 50w resistor is overkill! LEDs are likely to cause problems if the resistor is not well matched to the vehicle's requirements. Rather than fitting resistors, on older vehicles you can replace the flasher unit with an LED compatible one, or one that will accept both LEDs & incandescent bulbs if not all are being replaced by LEDs. More modern CAN-BUS wired vehicles are problematic, AFAIK they have no flasher unit so the resistors need to be close to whatever the original bulbs "drain" on the system was, otherwise the on board control unit / computer sees LEDs as a blown bulb & flashes too fast as a warning. Often the replacement LED bulb / lamp will have no specs so it is hard to calculate the correct resistance. This is particularly the case with motorcycle indicators which come as sealed units with an unknown number of individual LEDs & where you have no idea of their specs.

    On fitting a load resistor to correct hyper flashing.

    Once the supply (positive) wire has been spliced in, couldn't the remaining wire (negative) simply be earthed?

    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.

    4 replies

    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.

    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.

    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.

    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.

    I have a old 1971 motorbike a Hercules 125 BW (german army) and it has a 6 volt electric system,the system is rubbish and the bulbs burn out due to overload on the system a well known fact on these bikes.I want to convert the blinker turn signals to LED,and want to know what type of load resistor to install,or are they all the same?Will one for a car or motorbike with a 12 volt battery be ok,or due I need something differant?please help:)

    What exactly is this "merge" method? If you are just exposing wire from the light harness and wrapping bare wire from the load resistor and taping it, that doesn't seem very legit unless you are soldering the connection.

    Ok here is my question.. I have led taillights.. with leds an resistors every thing works great with reg bulbs up front.. now switch them over to leds an nothing well it flashes but very very slow.. do I need reisitors in the front to ?

    I hae tried all a,d still not working,


    Will these instructions still apply when using LED Brake replacements for a 7443?

    I'm wondering if anyone has tried using a 6 ohm 1 watt or 5 watt resistor instead of a 50 watt resistor. With these small bayonet bulbs, the current draw can't be much, so why put a $3-5 50 watt resistor there? Let the resistor wattage match whatever wattage the bulb draw is. Isn't the 50 watt a bit overkill in these places? I'd rather buy a box of 5 watt resistors, not the fancy looking gold ones.

    1 reply

    The 7443 bulb as an example has a 25 watt blink filament. It is using 25 watts when it is on so it is drawing about 2.25 amps - quite a bit of current actually. The power in the resistor is about 30 watts when it is on. It is on half the time, so the average power is 15 watts. A 1 or 5 watt resistor would fail right away unfortunately.

    I have one 3157 bulb turn signal. If I wanted to tap into the turn signal wire for a second bulb when I convert to led's, would I need two resistors for the same circuit? Or would I put one resistor in before I splice in the second plug will two led's work with just the 1 resistor or will it overload it?

    3 replies

    Hi, you'll need one resistor per each LED turn signal bulb

    Hey I'm wondering if I can get your help on wiring up my resistors to my 02 ram.

    Idk if I could send pics on this thing or what. But I've been reading these posts and you seem to know what you're doing. Maybe I can text you pics of what I'm trying to do?

    I've done this and will be switching out of T-taps. My only question is does the resistor matter where it would be mounted? Should it be screwed/tied/taped? I've used this item to take care of LED hyper flashing but I may need to diagnose another issue.

    I have a 1997 Jeep Wrangler TJ. I’ve had stock-looking LED brake lights already installed for some time now. They work fine. Recently, I replaced the two front turn signals with LEDs and I’m having problems. Both sides blink fast now. Even my dashboard lights blink when turn signal is operating. I know resistors are a necessity for such a product. I’m unsure what is causing the problem. Any help would be most appreciated. These are the LEDs I installed recently.