12Pin DRL Flasher Relay LED Modification (Another One)

Right off the bat many thanks goes out to @VE7OSR for validating the resistor value I needed. Based on his information hopefully others who are inclined can find the right resistor for their situation.

My 2010XR came equipped with DRL's. I stuck with incandescent bulbs for the longest time with no issues until my first set of headlights had their lenses melted by the DRL.

After purchasing new headlights I set out to prevent the lens melting again and decided on using LED bulbs instead. LEDs present a well known problem of hyper flashing.

To fix this issue I originally installed the 6Ohm 50Watt load resistors. 4 total (one for each signal position; 4 LED bulbs replaced; front and back).

This solution worked for the hyper flash but it didn't provide the bulb out hyper flash.

To get the bulb out hyper flash back I decided to modify the DRL flasher relay. Others have done this by grinding the shunt to fix the hyper flash but I personally didn't feel like playing guessing games on this. Another factor I considered was if I should ever need to go back to incandescents I couldn't use the modded relay...I would have to buy a new relay.

Since I would have to buy a new relay in the event I may need to, I figured I might as well buy a new one and modify that for LEDs and retain my stock relay for incandescents. These relays, new, aren't cheap but if you want to have the ability to return to stock quickly this is the better route.

Another way to retain stock function is to remove the stock shunt in its entirety and keep it in a safe place.

To modify the relay with resistors (as opposed to grinding) you need to determine your LED amp draw.

Since I was using the same bulbs (Sylvania ZEVO

$40 3157A /4157A ST BP SilverStar 27-Watt High Performance Signal Light

3157A and 3157R) for the front and back, I simply needed to verify the amp draw of one bulb.

My reading put one bulb at roughly 115.6/7 mA. Rounded up to 0.116A.

Courtesy of @VE7OSR

Alot of numbers there but the key numbers are the amp draw of the bulbs (117mA), the voltage drop across the stock shunt (0.075V), and the minimum voltage used to determine a bulb out scenario (0.049V).

The voltage drop and minimum voltage values, through research, pertain to the 12pin drl flasher relay (with one shunt) per @VE7OSR https://www.tacomaworld.com/threads/12-pin-dtrl-led-flasher-modification-2012-tacoma.244028/

Wow that was alot of information to get through. The quick and dirty is that you need to find the proper resistor value to match your LED amp draw to allow enough voltage drop for the circuit board to do its job and see a proper load for bulbs working or not.

So for my situation I ended up using (due to available local stock) a 0.33Ohm 2Watt resistor for 4 LED signal bulbs (two front; two back). After a week of driving every day (modded/installed the relay on 12August2016) my signals do not hyperflash, I no longer need "hot" resistors wired in parallel, and the bulb out hyper flash works when disconnecting one bulb from the circuit.

Overall I am happy with the outcome and hope this information helps others in the future.

There are many existing threads and pics on the relay location and removal so I will only add the pics of what I have done to this point.

It took me less time to remove the stock shunt, solder the new resistor, and connect the relay back into its harness than it did for me to wire 4 resistors. I also ziptied the relay to a spot out of the way but easier to get to than the factory location.

12Pin (2005-2011) DRL flasher relay part number


Stock shunt removed


Solder point on the underside of the board


Resistor installed

 

So what happens to this resistor when you connect a trailer light converter to this circuit and add more led's.

 

No change. The lights for the trailer are operated through relays. No further modification needed to the flasher unit, as the relay coil load is always part of the flasher load. The flasher only 'sees' the relay coil, not the actual current draw of the trailer lights.

ah, I see your thinking of adding an aftermarket versus using the stock trailer circuit.
In that case, yes any added load from the aftermarket unit would need to be taken into account, but i suspect the wiring for the trailer option is probably already on the truck, just need to add the relay in the engine compartment, and find the trailer harness connector by the bumper.

 

Where did you buy the resistor? So in theory, if only the rears were LED, then the resistor would be .66 ohm?

 

Depends on the LEDs you are getting, need to know their current draw. Resistors are available at electronic part suppliers; typically I give references to Digikey.com online catalogue items.

 

I found a local store that had circuit supplies; you can definitely find what you need online. As for the resistor value, you would need to determine the combined draw of the incandescent and LED bulbs that will be on the circuit.

Ditto. Online suppliers are usually my last go to if I can't find it locally.

 

A little help please...

First off, great thread! This is the route I want to go on my 2011. I plan on running sylvania leds 4157A for the front DRL/turn signal and the rear turn signal.

I’ll do the math tomorrow when I’m at work, but I’m hoping the numbers are similar to what you have. The help I need is that I can’t see the four images you uploaded in the original post.

 

Note that you need 3157CK for the front, and regular 3157 for the rear.
With these bulbs, each draws 0.05A, 2 bulbs flashing = 0.05+0.05 = 0.1A

Resistor in Flasher = .075V/0.1A = 0.75 Ohm
example part
https://www.digikey.com/product-det...nic-components/ERX-1SJR75/P0.75W-1BK-ND/35661

 

Thank you for the write up.

I did this mod today on my '09. It's my second attempt; the first time I put LEDs in the blinkers, I used the 6 Ohm load resistors. I didn't like it and undid the mod. Today I modified the blinker relay. At the end, it's a much cleaner install and might even be faster to do this than to mess around with the load resistors.

I changed out the front and read amber bulbs with Sylvania ZEVO

$40 Sylvania 3157A/4157A ST BP SilverStar 27-Watt High Performance Signal Light

3157A for the front and 3157R for the back. As you suggested, I replaced the shunt with a 0.33Ohm 2Watt resistor. It turned out to work great. One thing I noticed is that, when having the amber DLR on, the first blink is a "hyper" blink, the next blinks are at normal speed. When using the low-beams, there are no hyper blinks. It doesn't bother me though.

While I was at it, I also replaced the reverse bulbs with Sylvania ZEVO 921 LEDs. Same style as the 3157's

 

For those who can't solder on a circuit board, if you don't mind losing the DRL function, you can get a 12 pin to 8 pin adapter harness, Toyota part # 82241-35010, and a Smart tap 8 pin LED relay module. 10 minutes tops, plug and play, hazards and turn signals. The daytime running light don't work anymore, but I'm not melting the new headlights, either.