Bicycle Mechanics - Tire Generator Problem

I recently installed a new tire-driven bottle style generator on my 70s Samurai, but the tail light just won't work. I fiddled with the wiring, tried a different bulb, took apart the tail lamp assembly, but no luck. I tested the generator with a different tail lamp entirely and it still didn't work. Has anyone here taken apart a bottle generator and gotten it to work properly? Headlamp output works just fine, but the tail lamp doesn't seem to be getting any power.

I recently installed a new tire-driven bottle style generator on my 70s Samurai, but the tail light just won't work. I fiddled with the wiring, tried a different bulb, took apart the tail lamp assembly, but no luck. I tested the generator with a different tail lamp entirely and it still didn't work. Has anyone here taken apart a bottle generator and gotten it to work properly? Headlamp output works just fine, but the tail lamp doesn't seem to be getting any power.

These generators usually rely on the frame of the bike for one of the conductors, along with a single wire.

My guess is that there is not a good electrical connection either at the generator or the taillight.

If the headlight works there is nothing wrong with the generator itself. It's either the taillight or the connections from the generator to the taillight.

Sheldon "Ground" Brown

Get your multimeter out and test for continuity first, then have someone spin the he11 out of the wheel and test for voltage. Gotta have a bad connection there somewhere...

These generators usually rely on the frame of the bike for one of the conductors, along with a single wire.

My guess is that there is not a good electrical connection either at the generator or the taillight.

If the headlight works there is nothing wrong with the generator itself. It's either the taillight or the connections from the generator to the taillight.

Sheldon "Ground" Brown


Hit the nail on the head, Sheldon. I cleaned up the frame where the contact for the ground is. I also rewired the connection to the bulb a bit to make sure the ground and the live weren't touching- and it worked. Tail light works fine now. Thanks for the tip.