|
The turn signal indicator light is actually wired to the + of both front turn signals, based on the wiring diagram linked above. Voltage is based on the differential between the two wires, so this works since there's voltage on the blinker that's on, but not on the other one. When your right blinker is on, the gray wire of the dash bulb is + and the green wire is -. When the left blinker is on, the green wire is + and the gray wire is -. This also means that switching the dash bulb to an LED wouldn't work, since LEDs are polarized and will only work with the power flowing one way through them.
When you switch to LEDs which need much less power to light up, the little bit of juice going through the dash light to the other side's blinker is enough to also light up the other side. The only reason it doesn't happen with the stock blinkers is that the bulbs are so inefficient, the little bit of power coming to them isn't enough to make them light up. Personally, I think diodes should be added, even with stock blinkers, for a "proper" circuit.
You could also replace the dash bulb with two LEDs and a separate shared ground wire to give you and indicator for each side and inherently stop the bleedover between the two sides. Just run the existing bulb's green wire to the positive side of one LED and the gray wire to the positive side of another LED, and hook the LEDs' negative sides to a ground wire. The blinker will feed power to the LED on its side (left through green and right through gray) and through to ground, but power won't flow through the second LED (and therefore the blinker on that side) due to its polarity.
|