I have not seen any instructions for modifying this relay to use LED bulbs. I ONLY CHANGED OUT THE FRONT TURN SIGNALS TO LEDS, so these instructions may not work if you want to run rear LED bulbs too. I changed mine because the DRLs run so hot they burn up the bulb connector and bulb. I bought cheap bulbs from e-bay and had to file down the base so the width would fit.
12 Pin turn signal flasher relay with DRL (toyota P/N 81980-35020 Denso P/N 066500-5570)
It worked on my 2003 and 2004 4Runners.
Here are the steps:
1. Remove relay (
instructions)
2. Remove relay cover
3. Desolder R4 (200 ohm resistor marked 201. 201 = 20 followed by 1 zero) You can alternately heat the sides of the resistor with a soldering iron until it comes off.
4. Replace R4 with approximately 1.8K resistor. I used 1.82K. Ideally you have a size 2010 (5mmx2.5mm) resistor like the original, but I used a 1206 since it was all I had. I had to bridge the solder across gaps to make it fit. I determined this value by soldering on a 10K potentiometer and turning it both directions with the turn signal on. One direction the signal will fast blink, the other direction it will go crazy and then stop blinking. Measure the resistance at both extremes and then take the average for the new value. Note that you have to unplug the relay to measure the resistance as the resistor has voltage on it even when ignition is off, and this messes up the resistance measurement. I didn't measure the voltage to calculate the power, but 1/16th Watt is more than enough for 1.8K.
5. solder a new resistor for R4 (1.82K may work for you)
Here's my debugging in case anybody else wants to improve upon it.
There are probably 3 ways to hack this relay module for LEDs.
1. Change shunt. My guess is you could just exchange the 19milliOhm resistor with one twice as large if you run incandescents in the back. I didn't have such a resistor and didn't want to try to make one. You need the voltage drop to equal 75mV for the amount of current in one front and one back light. If you change the shunt, you also need to consider if it can dissipate all the power if somebody puts in incandescent bulbs.
Measurements courtesy of VE7OSR
2. Change R4 which sets the current sense level. This is what I did. However, I suspect this may not work for LEDs in front and back as the voltage drop across the stock shunt would be almost immeasurable. You could change R4 as well as the shunt to fine tune.
3. Possibly lift pin 1 of IC1 and fine tune a voltage about 75mV less than pin 2 to simulate the proper voltage drop across the shunt. I did not try this, and it would prevent detection of a failed bulb.
I deduced what I could of IC1 - Denso SE336
1 = Right indicator out
2 = VCC (12V)
3 = Left indicator out
4 = Right indicator in
5 = Left indicator in
6 = current sense level adjust (via resistor to ground) Originally 200 ohm
7 = no connect (9V when ignition on)
8 = Hazard indicator in
9 = ? (5V when ignition on)
10 = current sense (measures voltage drop from VCC across shunt)
The "indicator in" signals connect to the turn signal switch and hazard switch. They are pulled up to 12V when off and pulled down through resistors to 3.5V when on.