Headlamp problem - fuse keeps blowing

[Loudo]

OK guys, I have a real juicy electrical gremlin problem to sink your teeth into. 1963 CB77, replaced the headlamp. Also replaced the dimmer switch with a used switch off eBay. With all the wiring connected, and with the headlight assembly laying on the front fender lamp side down and backside wiring facing up, everything works fine. With the headlight switch in middle position, main switch on, only the neutral light is on. So far so good. Switching the headlight switch clockwise, now the headlight is on and I can toggle between high beam and low beam with the dimmer switch. Speedo lamp is on also. Again, no problem so far. With headlight switch at far counter-clockwise position, taillight and speedo and neutral lamps are on, with no headlight as expected. Still everything's OK. Now, here's the good part...I pick up the headlight assembly and hang it from the headlight bucket. Turn main switch on, neutral lamp comes on. Normal. Then when I turn the headlight switch clockwise, the neutral lamp goes out. It's because I've blown the fuse. I've gone through about four fuses repeating this sequence of events. I'm guessing I have a short somewhere that doesn't manifest itself until I ground the headlight to the bucket. I don't see any exposed wires, and the pieces of electrical tape you see in the pics are just to cover the exposed metal parts of the electrical connectors, they are not the outcome of twisted wire cob-jobs. Based on the information I've provided, can someone point me in the right direction? Clearly I'm not an electrical expert, just a dangerous character with a multi-tester.

[mike69]

I can see that you a blue wire connected to a red wire and a red wire connected to a blue. I'd fix that first.

[Loudo]

Yes, Mike you have a good eye. And I had a long story all spelled out explaining why I did that which caused me to take another close look at my wiring and.....discovered my problem. The new/old used dimmer switch I installed (which incidentally has a blue sheath instead of silver) did not have a brown wire like the original but had a green wire in its place. After threading this new harness into the bucket I think I confused myself when trying to negotiate all the green wires (power AND ground) and had inadvertantly connected the green ground wire from the headlamp to the brown wire from the headlight switch. I knew I was supposed to connect a green wire to the brown wire but I chose the wrong one.

Now it all works fine. Thanks, Mike!

My brain doesn't work so good what with only being able to work on the bike a few minutes here and there between hourly emergencies such as which window the lacrosse ball went through this time...

[mike69]

I know exactly what you mean. I've been there myself many times.

[e3steve]

Then when I turn the headlight switch clockwise, the neutral lamp goes out. It's because I've blown the fuse. I've gone through about four fuses repeating this sequence of events.

For testing situations such as this, attach a pair of croc-clip wires to the hi-beam (60 Watt) filament of an H4 headlight bulb in place of the fuse during test procedures (be sure to employ a 5-amp charger or, at least, a battery tender to support the consumption if a procedure takes longer than 10 mins or so). The lamp will act as a current-limiter, burning at full brightness whilst the short circuit is present; it will reduce in brightness significantly while less demanding consumers ~ ignition system, neutral light, parking lights, etc. ~ are being fed. You can then work your way back through your recent re-connections until the test lamp goes dim, thus pinpointing the source of the short.

[Loudo]

Thanks, Steve....I hadn't thought of that. Understandably, because despite all the electrical troubleshooting and repairs I've done over the years, it's not my strong suit. Accordingly I'm morbid and mopey when there's an electrical problem to figure out and ecstatic when the problem's solved. And how I get from one to the other is often something I can't explain!