LED turn signals not flashing.
Question
Hi, I’m trying to replace the bulbs (incandescent) on my motorbike’s turn signals with orange LEDs. I calculated the resistance of connecting 2 LEDs in series and sourced a resistor to attach, supposedly to replicate the same load as the OEM bulbs, problem is, when I test it the LED’s light up but just stay on constantly rather than flashing like they should.
I’ve tried numerous configurations to see where Im going wrong but the only results I can get are as described above, or not lighting up at all.
Here is my calculations taken from led calculator
Power Supply: 12V
LED voltage drop: 2.2V
LEd current rating: 75mA
Number of LEDs: 2 in series
And it says I need a 110 ohm resistor on the ground side of the LEDs.
Which is exactly what I’ve done.
Where did it all go wrong?
Thanks…
The simple answer is the voltage drop, two LED’s will not have a 2.2 volt drop.
But let back up and look at the big picture here. Normally an automotive turn signal system will use 2 to 4 bulbs per side, lets focus on a 2 bulb system. The most common bulb is the 1157 which has about 20 watts on the bright side per bulb for a total of 40 watts per side, this is the wattage that the flasher will “see”. Now if we use the calculator on Rushps.com we will find that we need to replicate the following;
we will need 3.33 amps with a resistance value of 3.6 ohms.
Now as I read the question it seems you are trying to run the power through the flasher to one led to the next led and then to ground. This a bit awkward, a better way to run this would be through the flasher then run one wire forward and one wire back, after each led then install two relays, one at the front and one at the rear. This would require a pair of 3 to 4 ohm resistor however you are going to need about 25 watts per led. This will get warm so you would want to use the resistors with a built in heatsink or one designed for automotive use. They cost around $10.00 or you can just buy a flasher designed for use with leds, they are know as electronic flashers or led flashers. In my opinion the electronic flasher is an easier way to go, but both should get your turn signals flashing again.
Leave a Comment