Originally Posted by
noglider
I'm not that handy with electronics, but I can solder. I've used multimeters, but maybe I need to learn more. My taillight isn't working, though my headlight is. I put an ohmmeter over the leads coming out of the headlight intended for the taillight. The beep indicates continuity, but it shouldn't, should it? But wait, there's more. I put the ohmmeter on the leads from the dynamo hub, and that beeped, too. But the hub works. 1. How is this possible, and more importantly, 2. how do I find the problem with this short circuit in place?
If the headlight's working, there isn't a short. That would pull the voltage down and the headlight wouldn't work either. Go to your tail light and use the 20volt a.c. scale on your meter.
If your tail light terminals have a voltage between them, the light is faulty, replace the bulb or the whole light if there's no removable bulb. If there's no voltage you need to check continuity on the live wire going to your tail light (the one that's insulated from the frame) . If that's ok then there's a bad connection to the frame. Some bikes use 2 wires to eliminate the possibility of a bad frame connection, in that case you need to check continuity of both wires. Tail lights often have poor quality touching metal connections, so I always bypass these and solder the wires directly to the inside of the light - if I can get into it. Hope this helps.