Using Automotive LED Lights is a bit different than using incandescent automotive bulbs. You can expect the wire colors and power consumption to be a bit of a surprise. Being that LED lights use far less power than standard automotive bulbs, if you plan to install LED lights as blinkers/turn signals, you should replace the standard thermal flasher relay with an LED or electronic flasher relay. LED bulbs use such little power that they won’t create enough heat to trip a standard thermal flasher.
With that being said, let’s get started!
LED Lights with only one wire will normally ground (-) through the base of the light housing and are going to be a single function light. This means marker light, running light, brake light or blinker. In this case the single wire whether the color is white, black or red will function as the positive (+) power wire.
LED Lights with 2 wires are generally going to be a single function light. This means marker light, running light, brake light or blinker. In this case one of the wires will be ground (-) and the other is positive(+). Generally a white and a black wire will be provided. The white will normally be the ground(-) and the black will be the positive(+).
LED Lights with 3 wires will be a multi-function light. They can (most times) be used in whatever configuration is right for your application. For example, running and brake, running and blinker or brake and blinker. These LED’s will usually have a black, red and white wire. In this case the white is ground(-), red is positive(+) and black is the second positive(+).
So for the LED’s with 3 wires being installed as brake and blinker – connecting the LED light’s black wire to the vehicle’s positive brake light wire and the LED lights red wire to the vehicles positive(+) blinker wire coming from the flasher relay would be correct.
Being that there is really no industry standard for wire coloring in these “aftermarket” LED lights, testing with a multi-meter is always a good idea. Most times the LED’s will include some details about wiring, but they don’t always.
Testing LED lights for proper polarity with a 9v battery is also a great way of determining which wires are positive and which are negative. For example, if you have a three wire LED light assembly, touch the suspected negative(-) wire to the 9v battery negative(-) side and at the same time, touch the one of the remaining wires to the 9v battery positive(+) side. If by chance you’re mistaken and end up with both positive wires connected to the 9v battery (LED + to 9v(-) and LED+ to 9v(+) ) no damage should occur.