Hitchcocks Forum

Try as I might to get a LED stop and tail light bulb to work in my back light I can't, standard bulbs work fine I have tried at least 4. The LED works fine across a spare battery on both terminals, plus the supplier sent me another just incase the first one was duff. I have had the light apart to check for loose terminals all seem ok, the 3 wires to the light are green/yellow to the side of the bulb (I assume earth), green to one of the bulb terminals, and dark brown to the other. So why does this not power the bulb if the standard bulb works and the wiring is correct.I hate electrics. Thanks for any help. 2010 EFI.

LEDs only work if the polarity is the correct way round the pos and neg must be correct were as ordinary bulls work either way round

Les how would I correct this or change the polarity? surely not at the battery. I have fitted an LED pilot light, and the 2 casquette pilots and they work fine.

Rosy swap the wires at the light fitting.

Or you'll probably find a connector somewhere on the wiring to the rear light. You could swap polarity there.

But there is three wires, 1 earth, 1 for tail light, 1 for brake light, forgive me if I am being a bit thick here.

Swap the TWO wires to each bulb/filament. One is earth one is live.

Ah yes, three wires, I see what you mean. Perhaps you have the bulb in the wrong way round? Anyway, a simple test with a voltmeter will tell you if it's the wiring or bulb which is at fault. Thinking about it, if the bulb works on a battery but not on the bike, and an ordinary bulb works - either the polarity is wrong or the bulb contacts aren't making contact.

No, don't swap wires, you'll just end up shorting the live to the frame! The bulb holder is grounded, and the so called earth wire (positive if pos.earth system)only ensures a good connection between frame and light fitting. I think you need positive earth LEDs........ there isn't an easy way of changing a twin filament bulb's polarity I don't think.

Hi P, I don't know jack sh1t about EFIs but my old nail is 12v Negative earth/ground