Rear running light not working

[SangreDeDios]

so I got an 81 that's giving me some problems with the rear taillight, the brake light lights up fine but the running light will not light up.
I've tried different bulbs and a whole different taillight so the problems is before it hits the taillight harness.
Anyone know what exactly powers the exterior light? Trying to trace these wires is a biatch.

 

[hmusket]

Assuming you have the standard wiring harness, the blue wire powers the rear light. Try this: Disconnect the tail light from the harness. Using a 12v circuit tester put a probe into the blue wire connectors (I think there's one for the tail light and one for the License plate light) on the harness, one at a time, and ground the other end somewhere on the frame. Turn your ignition key to park and see if the circuit tester light comes on. Try it for both wires. Here's a link to the wiring diagram for 1981 View attachment 529
"L" is for blue. Also, like its been said many times, make sure all your connections are clean and tight.
One more thought, if you're going to leave your ignition on for a while it might be worthwhile to unplug your TCI.

 

[shotgunjoe]

I was just doing this last night... it worked before I removed the ignition for relocation. Turns out the ignition switch itself powers the running light.

 

[SangreDeDios]

hmmm interesting you say that because my ignition switch is gone.
The bike is wired to an on/off toggle switch.

So how does it work with 2 fillaments, sorry my electric knowledge is miniscule.
Would there be a separate wire powering each, like one for the brake light and for the exterior light?

I'll also be trying what you posted hmusket.

 

[hmusket]

Well, ignore what I said, since you're not using the ignition switch, I think you would be wasting your time. Instead, what you have to do is find a way to power the blue wire when you toggle the switch on. All you might have to do is splice it to the brown wire connection. I'm assuming on your switch one side is the brown wire, the other is the red wire?

 

[shotgunjoe]

 

[Gordon]

Your going to need to wire in a headlite switch, on & off. Then wire into that, or get a stock ignition switch.