A maze with no exit (brake light wiring)

[misterprofessionality]

misterp, don't want to assume anything. You are grounding the body of the new light, right? it isn't being insulated from the fender somehow?

Ben

I'm not dreadfully familiar with these things, but since you're asking, the fender has a powder coated paint job on it. would that serve to insulate it?

does it fail to work at all without a proper ground connection?

[pekingduck]

Thanks, pekingduck, that makes sense. Except that with the Honda OEM light, surely it completes both circuits? How is that supposed to happen with the new arrangement?

Yes, the green ground wire is necessary to complete both circuits on the stock taillight because it has a plastic taillight bracket rubber-mounted to the stock steel fender. (The chrome plating on the plastic is actually conductive).

But the aftermarket light gets its ground, assuming the base is metal, when it is bolted solidly to the steel rear fender, in turn grounding to the frame.

[Ben70_imp]

Ground is as important as power in a circuit. Try grounding the unit to a bare metal engine part with a jumper wire just to see what happens. Or to battery ground.

Ben

[Cormanus]

Yes, misterp. If it isn't grounded, the circuit can be completed and will not work. I confess, I'm still struggling to figure out the wiring diagram, but then I know little about these things. I can't tell you whether powder coating would insulate the fender.

Apologies Ben70 and pekingduck. Seems we posted simultaneously. I think I'm beginning to get it now.

[Ben70_imp]

Great minds...

Ben

[misterprofessionality]

Ground is as important as power in a circuit. Try grounding the unit to a bare metal engine part with a jumper wire just to see what happens. Or to battery ground.

Ben

This has yielded no results. i tried to ground it all over the bike using a jumper cable i had laying about. i clipped the green wire to it and tried to hook the cable in various spots on the bike to see if it would produce a result. no dice.

[Ben70_imp]

The black/brn wire is powered by the ignition, for you running light. the green/yellow is to the brake light switch. The green is your ground wire. it won't power anything. However, if you can connect it to your light via the mounting bracket screw it may provide your ground for your new light.

Ben

[pekingduck]

Ground is as important as power in a circuit. Try grounding the unit to a bare metal engine part with a jumper wire just to see what happens. Or to battery ground.

Ben

This has yielded no results. i tried to ground it all over the bike using a jumper cable i had laying about. i clipped the green wire to it and tried to hook the cable in various spots on the bike to see if it would produce a result. no dice.

This has yielded no results. i tried to ground it all over the bike using a jumper cable i had laying about. i clipped the green wire to it and tried to hook the cable in various spots on the bike to see if it would produce a result. no dice.
You are grounding the harness ground to ground.

With the red and black wires connected to the new taillight, run the jumper between the base of the new taillight and the green wire.

[Cormanus]

Would powder coating limit conductivity? Yes, I know it's irrelevant, but I'm interested.

[Lord Popgun]

Cormanus,

It will. And regular paint too. A good clean metal to metal contact is required.