I have figured out a low cost solution for automatically switching the 100% brightness to the 50% on the 2011/2012 headlights for the 06-10 models that have upgraded their headlights.

First we will start with a very common relay (R51) used on thousands of applications.
this relay is a 5 pin relay availible just about at any automotive retailer. The average cost of this relay is around $8.00. Tools needed for this project are very basic.

1. Wire strippers/cutters
2. Terminal crimpers
3. 16-18 ga. wire
4. blade terminals.
5 Heat shrink or electrical tape (I prefer heat shrink)

Pin 30 and pin 87a are normally closed (allowing power to flow through the relay to the 100% brightness. The relay is de-energized at this stage. Once power is applied to the coil (pin86) it will move the contact to pin 87, therfore opening the circuit to the 100% and supplying power to the 50% brightness.

You will have a wire coming from the IGN2 fuse to Pin 30.
You will have a wire coming from pin 87a to the 100% wire (green)
The 50% wire (black) will go to pin 87.
Pin 85 will go to ground.
Pin 86 will be power to energize the coil to actuate the switch. You will use power from the parking lamps to pin 86.
Most all relay have the diagram on the side .Follow the diagram on the relay but all should be very similar.
Do this mod at your own risk. Neither I nor Club Lexus will be responsible for any damages.
I hope this helps all you fellow Lexus owners.

 

humm... very interesting!
thank you for the DIY!

 

Your welcome.

The R51 relay comes in different amp ratings. For this particular application I chose the 30amp capacity. LED's run on low voltage but pull a lot of current (amps) Also this single relay should have no problem operating both circuits on the headlamp LED's

For those who dont know, Here is a little theory on how relays work.

A relay is an electromechanical switch. More importantly, relays are used in virtually every type of electronic device to switch
voltages and electronic signals. The most common electromechanical switch is a simple wall switch used to control the lights in your
home. The difference with this type of switch is that wall switches require a human to perform the “switching” between on and off.
Relays operate differently. Relays require no human interaction in order for the switching to occur. In fact, electronic pulses actually
perform the switching. Relays are very powerful devices in the fact they can be used in virtually every industry: your automobile,
telephone systems, medical devices, and yes - car stereo systems.

 

I wanted to post a little more details on this DIY. I have done this mod myself and it works perfect.
First step will be to wire both LEDs together, both black and green. Dont cut the white one its the ground. After splicing the green(100%) wires together you will connect this wire to pin 87a.
Next after splicing the black wires (50%) together you wil connect this wire to pin 87
I'm using the Sewell headlights, so after you have cut the green wire from the LEDs the green wire that was tapped into the parking lamp will go to pin 86 of the relay. So when you turn on the parking lamps this will energize the coil switching the circuit from 87a to 87 there for opening the circuit for the 100% and closing the circuit for the 50%. From the fuse box under the hood locate IGN2, run a wire from IGN2 to pin 30 of the relay. The last wire to be connected is a ground to complete the circuit. I went from the chassis to pin 85. Be sure and remove any paint or grease to insure a good ground. Also when you purchse the relay ask for the socket that it plugs into this wiil make replacing the relay if needed a lot easier. I installed the relay in the relay box located next to the fuse box. I drilled a hole in the side towards the bottom and installed a grommet for the wires to pass through and still keep moisture out. last but not least install some plastic spiral conduit to make it lok factory. I will post some pictures to show the end result.

 

The relay wired

 

100% and 50% brightness

 

The conduit installed in to the relay box.

 

Also one last thing, The wire used to run this circuit can be purchased at Auto Zone/Wal-Mart.
believe it or not its trailer wire, I chose this wire because it has mostly the correct color wire. It has green,white,yellow,brown so you won't get confused to what wire goes where. Unfortunately it does not match the wire color on the socket of the relay.

 

Good write up, maybe i'll rewire my LEds for that purposes when i remove my bumper to fit gap

 

I smell a sticky?

 

This should be helpful to everyone who converted. I remember reading this was an issue for many

 

interesting, would like to try this, i think i will let my mechanic figure it out from your diagram, thanks for the info

 

https://www.clublexus.com/forums/is-...ml#post7177143

Jeff

 

I thought the 2012 headlights have the LEDs on 100% out of the box?

 

^ i believe this mod is from 100% to 50%..haha