How to: Modify your cars flasher unit to work with V-LEDS

Posted: December 2, 2010 in How to:, Technical, Trouble Shooting
Tags: , , , , , ,

Before we get started  I need to preface this article with a disclaimer. This is not a modification that should be attempted by everyone. This is only a guideline for those who fully understand how what they are trying to accomplish. V-LEDS cannot be held responsible for any damage that occurs to your vehicle while performing this modification. With that out of way lets get started.

This modification is relatively simple. I have done this before in the past, but never really thought much about it because we offer electronic flashers and load resistors that fix hyper-flashing issues. But what about the cars that we don’t have an electronic flasher for? Or for that customer who does not want to splice load resistors into his wiring harness. You can also look at this from an efficiency viewpoint. LEDs are very energy efficient and load resistors burn power to create an electrical load to trick the flasher unit, this defeats using the LEDs for this purpose.

Lets cover why you would even do this in the first place. We do not offer electronic flasher units for every car or truck out there.  If you happen to own a newer Honda/Acura you know that already. It is pretty spendy for the GM vehicles that use the LM487 flasher and Lexus vehicles lose the confirmation light flash of the security system when you replace the flasher unit with and LED compatible version. What if you could just modify the flasher unit that came in your car? How would you go about doing it? Before you modify anything you should probably understand how it works. Lets start with understanding how the flasher unit knows when your bulbs burn out.

As with any electronics, flasher units function within a set of rules. These rules are pretty simple when it comes to a  flasher units hyper-flashing circuitry. The rule here is wattage and the flasher unit is looking for a specific value of wattage. The flasher unit monitors the wattage of both blinker circuits (any car that uses these style of flasher units will  have 2 blinker circuits, a left and right) and compares the value of these circuits to a resistor that is located on the circuit board of the flasher unit. The resistor is a metal “HOOP”. This hoop is designed to be within a specific wattage range, anywhere from 42-54 watts depending on the wattage of your cars original blinker bulbs.  See the diagrams below to see what the hoop looks like. Depending on your vehicle, it  may look different from these examples.

Toyota/Lexus Flasher Unit

Typical Ford Flasher

So now that you understand how this part of the blinker circuit functions we can start to understand what needs to be modified in order for it to work with V-LEDS. We already know that LEDs have an much lower wattage draw than the filament bulbs. Another factor to consider is that an LED actually stops voltage. LED is the acronym for Light Emitting Diode, and diodes do not carry any electrical resistance (OHMS) across the positive and negative contacts. This changes the value of the blinker circuit and the flasher unit recognizes this as a burnt out bulbs and starts to hyper-flash.

This simple modification will allow you to change the value of the flasher units resistor hoop to match the value of your V-LEDS. After you have removed your flasher unit from your car and removed its cover take a look to see if yours has the resistor hoop. If you find that yours has the hoop you can go ahead and start, the process is pretty easy. All that needs to be done is to remove some material thickness from the hoop. This will change the value of the hoop, and by doing so changes the value to match that of your V-LEDS. You can use  a dremel tool with a sanding drum or something similar to do this, either way you do it be sure to take your time. Be sure you do not overheat the hoop, you can melt the solder joint on the circuit board. Grind small amounts of material off of the hoop. I ground down the face of it first and then ground down the top of it. Reinstall the flasher unit and test the blinkers periodically to ensure that you get it just right. While tested I found at one point the blinkers were flashing normally for about 5 seconds then would go back to hyper-flashing for a few seconds and  would continue to go back and forth. I ground off just a little more and it worked flawlessly. If you get this just right the flasher unit will function the same as it does with the filament bulbs. This means that if one of your V-LEDs stops working for some reason the blinker circuit will hyper-flash to let you know. That is what I consider a bonus!

The process is really quick and painless.  After I removed the flasher unit it only took about 15-20 minutes to grind it down while testing it. After about the 5th time I got it perfect. It is a pretty straight forward job once you understand what needs to be done. The picture on the right shows how the hoop should look when it is complete. All that’s left to do is to place the cover back on the flasher unit and install it in the car.

Go ahead and test it out for yourself and see how it works. Let me know if it works for you too.

Thanks for reading. Feel free to leave a comment or ask a question, or you can contact me directly via email:

James, the

  1. Rich B says:

    What about a GM (Chevy Avalanche) flasher unit?

  2. MYRONCUZ says:

    i have the 6ohm resistors for my rears, if i do this, i would need to take them out correct?

    thanks james!! u da man!!

  3. Thanks Myron. Yes, remove the load resistors before you start.

  4. Matt says:

    If I do this modification will it burn out the flasher if I hook up a trailer that uses regular bulbs to my truck?

  5. I have not tested this specific situation myself. I do not think it would, as the hoop of the flasher is not a part of the circuit. The relay that is built into flasher can handle the wattage without problems, especially if the wattage has been reduced with the use of LEDs in your truck.

  6. Dennis Krause says:

    When I try to read what is in the red print on the photos by enlarging the image, the red print get all blurry.
    No I have not been smoking or drinking anything illegal…


  7. Sorry Denny, I had been saving some of my diagrams as JPEG files and it was blurring the RED color. I since have started saving as PNG files and that problem has gone away.

  8. Johnny says:

    Do you know if this would work on my 2010 Tundra?

  9. Ross says:

    Thank you James, was easy and works well, my son fitted LED lights to his rear 2004 Hilux ute. only took us a few goes it’s working correctly.

  10. If done correctly, it should work with any thermal flasher. Use at your own risk!

  11. klyuen says:

    Hi James:
    1:This method is take thickness to increase Restistor?
    2:This will work on my 1998 Buick Park?
    3.If I use 10W LED. Can I just take 50% OFF?

  12. […] a picture of how much material I needed to remove to stop hyperflash or hyper-flash from occurringHow to: Modify your cars flasher unit to work with V-LEDS V-LEDS. __________________ 2010 Iceberg White FJ "StormTrooper" 20" Black Rhino 33 […]

  13. Hi,
    It will work on most flashers, this is not “vehicle specific” – use at your own risk!

  14. kingkevinn says:

    i want to do this to my ford escape 2008, i was curious if you know how to get to the flasher unit? i dont want to damage my car trying to find it. also since this is post was referring to a ford unit, do you think this would work for my ford?

  15. V-LEDS says:

    I believe in the new Ford vehicles the flash rate is built into the BCM (body control module). This cannot be modified as it is built into the computer system.

  16. ArkanDan says:

    It’s my understanding that the flash control for the turn signals in the newer Fords is in the SJB (Smart Junction Box) located between the seats on the floor of my 2008 Mercury Mariner. No known modification to this unit. Would be interested in finding out otherwise if there is. Not sure if the 6 ohm load resitors are applicable either. Have been looking all over and finding very little usable information.

  17. V-LEDS says:

    You cannot modify the junction box on Ford vehicles. The load resistors will work to fix the flash rate of the blinkers after replacing them with V-LEDs. Use 6 OHM if you are replacing one pair of blinker bulbs, use 3 OHM if you are replacing both pairs of blinker bulbs. If you have any more questions send us an email at, we are quick to respond.