I'm stuck with a basic electric problem, on my honda cb500. The rear light bulb is a twin-filament for position/brake, 12v 5/21w. It's brand new and tested. The battery has 11.9v.
On the rear light connector, without the light bulb, I get 12v on the brake light wire, but as soon as I put the bulb in, it does not light up, and the voltage drops to 0.00v.
The position light works nice, without any voltage drop.
I don't have any clue on what could be happening, and testing the whole wire harness would take a lot of time, so I'm looking for any suggestion!