Wiring a new tail light

[JimmyR]

Just wondering if anyone knows which way around I should wire my new (not OEM) tail light. I have a beautiful new light from Japan but the instructions are entirely in Japanese so I'm not even sure that my question would be answered in them!

There are 3 wires - black, blue and green. I would guess that green would be ground, and this seems about right because because if I connect a 9V battery neg>green, pos>black or blue then the light glows. Black is brighter than blue, and when I look at the bulb you can see that the filament for the black wire is thicker. So is black for the brake or is blue?

[Steve]

And if you choose the wrong wire for the ground, you will simply get some rather strange results.

Your best bet will be to open it up, remove the bulb and use an ohmmeter to find out which wire is what. Touch one meter lead to the outside of the socket, find out which wire then completes the circuit. Now at least you know which one is the ground. For the other two, you can put the bulb back in, connect the ground, then touch the other two wires to a power source and see which one is which.

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[JimmyR]

Thanks guys!

[argonsagas]

And if you choose the wrong wire for the ground, you will simply get some rather strange results.

Your best bet will be to open it up, remove the bulb and use an ohmmeter to find out which wire is what. Touch one meter lead to the outside of the socket, find out which wire then completes the circuit. Now at least you know which one is the ground. For the other two, you can put the bulb back in, connect the ground, then touch the other two wires to a power source and see which one is which.

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That is pretty well all you need to do. If the new light is not yet attached to the bike you can simply move it near your battery, put the newly-found ground wire (apparently green in colour) to the negative terminal then try the others on the positive terminal and see which wire causes the bulb to burn brightest. That will be the brake light...(likely the black wire, since it seems to be attached to the thickest filament)..