Topic: tail light won't work

[professor]

Get this. My tail light works with brakes but does not work with headlight in the normal on position with headlight. It also works in the lights on position--the second position of on. I replaced the switch having thought that was the problem. Any ideas? Each length of wire I check says it gets power.

[TwoTired]

Check you 12v return path. Each electrical consumption device needs two connections to the battery. + 12V is only half the path. You need 12V return, too.  Some call it a ground. (though technically, it isn't)

Cheers,

[professor]

Thanks for the idea. Everything I read says most electrical problems are the ground. I'll try that.