Strange headlight problem

If it's broken or just needs tweaked

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Posts: 48
Joined: Tue Apr 15, 2014 3:16 pm

Strange headlight problem

Postby ScottBowl » Tue Jun 05, 2018 1:47 pm

Hello everyone!

I have a 1979 cb650 with a dead headlight problem. I'm already ruled out the bulb itself, so I got to checking this wiring diagram for the answer

I decided to follow the path of the power starting from the ignition switch to the fuse box. Good voltage on both sides of the headlight fuse, so then I cracked opened the right controls/throttle assembly and probed where the black/red wire ends up transfers power to the blue/white wire going to the high/low switch when the starter button is free. Voltage was present all the way to the high low switch itself, so I took that apart too and found that
the blue/white wire has voltage too! I then used a little piece of wire to jump to the white or blue pads to rule out the actual moving switch (for low and high beam) and to see if it would either burn the fuse or turn on the headlight, but neither happened when bridging the pads together like the switch normally would...

So then, I thought check for continuity. The white and Blue wires each tested good going from the switch to the headlight connector, however for some reason blue had continuity on both the blue and white pads at the switch... I then checked for ground and noticed the green wire at the connector tested good to the negative terminal of the battery, but then so did the blue wire!! Meaning the blue wire has a dead short to ground? But doesn't burn the fuse? The horn is also not working on this one, if that's somehow related. Turn signals and starter work fine.

Any thoughts very appreciated!

Posts: 48
Joined: Tue Apr 15, 2014 3:16 pm

Re: Strange headlight problem

Postby ScottBowl » Tue Jun 05, 2018 5:13 pm

Update - It was the switch, or more specifically the little square copper piece inside the switch that brings the source (blue/white) to the white or blue wires.

Posts: 4
Joined: Fri Jun 01, 2018 2:15 pm

Re: Strange headlight problem

Postby ts354 » Sat Jun 09, 2018 10:52 am

Its amazing that those tiny little copper pads that just brush up against another tiny little pad (exactly level with the plastic that holds it in place) are what "drives" the head light. I can see for the dash lights and stuff, but for your headlight???
I'm thinking of buying one of those Chinese handle bar controls - for 16.99 it should be a good test to see how easy it would be to wire up to the ends in the headlight bucket.

Or, I might try filing down the plastic on the switch that holds the pads.
Or, I might try a three way switch or something similar.

Off to radio shack.

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