Topic: Tailight wiring

[AlekStooge]

1978 CB 550K. I have an aftermarket taillight and I am having trouble getting the running light and stop light to work. I had it working before but I haven't worked on my bike in months, got busy with other stuff. The red is coming from the fuse, the yellow is going to the front/rear stop switches and black is supposed to be ground.

Everything checks out as far as I know. Maybe its not grounded right the black wire was originally where the other two are, but ripped out. Wasn't sure where it went back in there.

Any help appreciated.

[Mantree]

Bad bulb? Clean your ground? My first 2 steps

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[calj737]

If the black wire in your picture has been located to the mounting stud by you, and originally was inside the rubber housing, then your bulb socket is no longer grounded. Remove the rubber grommet and resolder the black wire correctly.


To confirm operation, simply touch the black wire as it is directly to the battery NEG and the Red wire to battery POS. If it lights, you're good. If not, you know the black wire is a problem as wired/shown.

[AlekStooge]

I not sure what to solder it to. I don't see anything in here that I could solder it to. Could it be that spring/coil looking thing in the first picture?

[madmtnmotors]

So you ripped a wire out and now it won't work? Did it work before the wire was ripped out? 

Put the fixture back together (with a known good bulb), grounded to the case just like you have it now. It looks like the metal socket is affixed to the metal case so grounding the metal case should work, unless the socket is isolated from the case with rubber or fiber washers. A simple continuity test would confirm whether the socket is grounded to the case.

Touch the wires directly to the battery, black to ground and red to positive. This will test one filament. To test the other filament touch the black to ground and then touch the yellow to positive. This will provide a definitive test for the light only and prevents any confusion that might arise based on a faulty switch or faulty wiring. Then when you hook it up to the harness you'll know the light is good, so if it won't light when connected to the harness you'll know you're looking for a faulty switch or faulty wiring at that point.

[AlekStooge]

That was very helpful thank you. The continuity test worked in both situations so there must be something wrong at one point in the harness. I going to revise my harness and find the issue.

[madmtnmotors]

That was very helpful thank you. The continuity test worked in both situations so there must be something wrong at one point in the harness. I going to revise my harness and find the issue.

Did you test the light by connecting it to the battery? The fixture is quite simple, but to troubleshoot electrical problems you often need to determine what it's not.

So remove the taillight from the list of potential culprits by connecting it directly to the battery and confirm that it works properly, then move to the next item.

[AlekStooge]

Yes that is what I did. I looked at the wiring later and everything made sense maybe a wire is loose somewhere. I'll have to further look into it.

By the way is this the front stop switch?

[evanphi]

Yes that is what I did. I looked at the wiring later and everything made sense maybe a wire is loose somewhere. I'll have to further look into it.

By the way is this the front stop switch?

Yes