12-pin DTRL LED Flasher Modification (2012 Tacoma)

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

 

You’re the man! Follow up: what is the difference between the 4157 pictured and the 3157CK? Pardon the ignorance, I’m not familiar with these bulbs.

 

The difference between CK and non CK is how the sockets are wired. With incandescent bulbs, it doesn't matter which direction current flows through the bulb. With LEDs, it does matter. This pic shows how they're wired and the direction of current flow. To simplify things, if the bulbs aren't marketed as CK, they're not CK.

 

Ok, polarity is important with leds, got it. Next question: Can I run the 4157 in the rear (since I already bought a pair) and the 3157CK in the front? Also, what’s your take on the 25 turn adjustable resistor? I’m seriously considering going that route just in case there are any future changes.

I was playing around today, and when my 4-ways are on they do not hyper flash.

 

Yes, you can run CK or non CK in the rear turnsignals. There are only 2 contacts in the rear turnsignals, so it doesn't matter. However, the rear tail/brake lights must be non CK.

I have no experience with resistors or modifying the DRL flasher. I chose to eliminate the DRL and install the Diode Dynamics smart tap LED flasher.

 

My DRL/Turn signal bulbs in the front only have two connections for the bulbs, only 2 wires going in, only two connections on the bulbs.

 

In the socket, there are 4 terminals. 2 of the terminals are connected together for ground. That's where non CK LEDs end up having a problem.

 

In short, get the CK type for the front.

 

If your flasher unit only has 8 pins, then there are LED capable flashers available, such as the diode dynamics model. IF your flasher has 12 pins, then you have the Daytime Running Light (DRL) model, and there are no aftermarket flashers that can handle LEDs available that I am aware of.

The modification to the resistors applies either way to 8pin or 12 pin stock flashers. Yes you could use a variable resistor. Highly recommend a multi turn model in the example shown, and a value ideally no more than a factor of ten from where you want to be, in your case closest value is likely 10 ohm, multi turn.

 

Thanks guys, really good info you’ve shared. I appreciate it a lot. I’ll grab some CKs for the front and see if my local radio shack has the variable resistors, if not I’ll order them

 

Ok gents, I put the 2 non CKs in the back.
I got the lower steering column shroud off.
I’ve removed the blinker relay from the vehicle, and in turn removed the cover.

It would appear I’m looking at a single shunt resistor. Can I still proceed using only one of the adjustable resistors pictured? I bought two.

 

I did just find your comments in https://www.tacomaworld.com/threads...ck-drl-flasher-and-no-resistors.176904/page-7

Looks like we have the same relay.

 

Ok, couldn’t wait, had to try it. Soldering went well. Time to plug it in and adjust it!




AND IT WORKS!!! I have the regular incandescent bulbs in the front, so I’ll have to adjust it again when the CKs get delivered. Leaving the steering column shroud off until then.

 

Sorry I didn't get around to this comment earlier, but yeah it's all the same I dunno why they switched to a double shunt style in some years. Glad these trimpots worked for you man!

 

I have an extra trim pot resistor (the same one I used) BNIB if someone needs it. $6 gets it shipped to you.

 

just spent the weekend modifying the flasher circuit in my '09 Tacoma. I never could get the shunt resistor set correctly so that both the emergency flashers and the turn signals would blink correctly. There are a few problems with trying to sense current on LED turn signals:
1. LEDs are active circuits, not resistive, so there is a large power draw when first turned on, which quickly tapers. The sensing circuit only samples the voltage across the shunt for a short time, which could explain why it is difficult to get the value right
2. Current draw varies a lot from one LED manufacturer to another, so changing LEDs in the future could cause the circuit to hyperblink again, or not blink at all.
3. When an LED fails, the driving circuit will most likely still draw power, so it is not possible to detect a burned out LED bulb by sensing the current draw, thus hyerblinking won't work to indicate a bad bulb.

Because of the above, I decided to "fake" out the controller circuit by providing it with a constant voltage through a potentiometer connected between +12V and ground. I used a 10K pot I had laying around. I lifted pin 8 on the little controller chip and soldered the middle wiper of the pot to that pin. Then I adjusted it until the blinkers and emergency blinkers worked correctly. The correct voltage to the pin was about 0.08V below +12V. Pics are below. The big resistor in place of the shunt wire was my last attempt at using shunt resistors.



I had a heck of a time trying to remove the module from the plastic fuse box. I finally ended up ripping it off, breaking the plastic retainer clip as shown below. I suppose I will just tie-wrap the module to something to finish up.

 

Not Bad! Trimpots definitely seem the way to go. Glad I didn't deal with running to a store 10x to find the right resistor pair

Update: After having my blinker on for like 3 minutes at a LONG light it started to hyper-flash. Will probably need to turn the pot just a hair but that's why this is such a great option. Also heard that pots will slowly change resistance as they age and wear from the current

 

Corrections,
1) Yes, LEDs are considered active components, but they do not have an in rush current when first turned on, then taper off - that is incorrect, and has no impact on the value of your resistor.
2) Yes, the aftermarket type of bulb you get, specifically how its built/combining several LEDs together does determine its overall current draw. If you order the same bulb type from the same manufacturer, you will get the same current draw within a very small percentage, that will have little effect on your resistor value.
3) Yes you can get the hyperblink warning for when an LED bulb fails, but not likely if you are calculating a resistor value to use when mixing incandescent bulbs with LEDs. (eg front are LEDs, rear are incandescent.)

The challenges folks are having using a trim pot (multi-turn, adjustable resistor) is that they are choosing a value such as 10,000 Ohm adjustable which does not give them the precision to get to the value needed, when the resistor value they need may be less than 1 Ohm. You would want the trim pot to be no more than a factor of ten of where your resistor value should be. (eg perhaps you calculate you need 1 Ohm resistance, maximum trim pot value should be 10 Ohm.)

 

Just did this mod on my 2011 DCSB using the Bourns 10ohm 25 turn 1W trimpot. I have LEDs front and rear. My flasher unit only has the single resistor. I was able to trim things up nicely to work in all different modes while the engine was running (turn signals with and without headlights, hazards, etc). My problem comes when trying the hazards with the engine off. It blinked once and stopped indicating too much resistance. I trimmed it to work but then had hyperflash when going back to engine running with turn signal.

I’m thinking the battery voltage drops slightly with the engine off and its enough to push the sense level beyond the sweet spot. Anyone else encounter this issue? Ideas? I can try fine tuning it some more but even if it works the sweet spot will be very narrow and things will likely drift out as temp changes.

It was posted earlier that measured voltage drop across the resistor was .075V for turn signal and .143V for hazards. Does anyone know how the circuit accomodates these different levels? In other words why isn’t .143V seen as a high resistance and then only blinks once? Maybe I accidentally messed something up when i was in there with the soldering iron.

Appreciate any help, thanks.

 

I was able to work with the trim pot in very small increments and find a position where everything is working with the engine both running and stopped. Need to use it a while to see if it’s going to drift out.