Headlight switch ground?

[oceancargo]

Hello All-
Scratching my head here. After a blistering high-speed run on my 305 scrambler I turned left onto another highway and the engine died. The fuse at my battery had failed and continues to fail ten seconds after replacement. At this point I've got my battery out and have disconnected the handlebar switch, the headlight, the rear brake switch and the stator wires. Measuring a ground between fuse outlet and frame with the ignition key switch in the middle position and the headlight switch left or right of center. Ground goes away when headlight switch is in center position.

Am I on the right track?

Thanks in advance

Trey

[DJM]

You're clearly on the right track, headlight itself or at least in the wiring between the dimmer switch and the headlight, try the same test with the wires disconnected from the headlight unit.
Could be the wires are twisted together and shorting in the switch itself but clearly clearly in the headlight area! Charging circuit faults shouldn't be able to blow the fuse unless you have something really odd going on.

[OldStan]

Hello All-
Scratching my head here. After a blistering high-speed run on my 305 scrambler I turned left onto another highway and the engine died. The fuse at my battery had failed and continues to fail ten seconds after replacement. At this point I've got my battery out and have disconnected the handlebar switch, the headlight, the rear brake switch and the stator wires. Measuring a ground between fuse outlet and frame with the ignition key switch in the middle position and the headlight switch left or right of center. Ground goes away when headlight switch is in center position.

Am I on the right track?

Thanks in advance

Trey

Tail light bulb is in circuit when headlight switch is left and right of center, so could be showing ground through it and/or wiring to it.

[DJM]

But surely the tail-light is still in circuit when the headlight switch is in the centre position too.

If the problem dissapears when the dimmer switch is in the centre position then surely it can't be an issue with the tail light can it?

[OldStan]

Taillight is off in center position of headlight switch . Left is taillight only, center is all off and right is headlight and taillight. If the switch is left of center the headlight (and dimmer switch) is out of the circuit.

[DJM]

Sorry,

I'm mixing up the LIGHTING switch with the dimmer switch which also has a centre OFF position on many early bikes although this was deleted on later models which just have Hi / Lo beam positions

I don't think U.S. models have the front 'pilot' light which we have in the UK so, yes you are quite right, only the taiil-light (and the speedomometer light! ) is in circuit with the LIGHTING switch in left or right hand positions, look there for the fault. Worth checking the bulb holder for the speedo light first as these aren't very substantial, to test just drop the bulb and holder out of the speedo case and see if the ground fault goes away.

Does the brake light work OK

[oceancargo]

I may have touched too many things at once to conclusively narrow down the source of my ground but I think I solved it.
I was concentrating all my efforts on the lighting switch. I had it in my head that because I had zero ohms across the black and green that was my ground. I forgot that DC circuits all go positive to negative, so it made perfect sense that I had zero ohms across Black and green.

Before I had that realization, I cut off the factory sheathing on the lighting switch wires looking for signs of short/ground there and then something about the rear brake light switch caught my attention. I disconnected the rear brake switch, reconnected the headlight switch to the harness and tested for ground with the lighting switch in the left position in the right position and was ground free.

Connected stop switch wires to frame and caused ground.

Taped up brake switch wires and rode 300 trouble free miles this weekend.

Thanks for the support,
Trey