intermittent electrical issue

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AMechEng

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My headlight is going out. At the same time the gauge illumination goes out. To make the lights turn on and off I turn the handlebars. Any guesses at the cause? I keep looking at the electrical schematic and I'm coming up blank.
 
The diagram shows a common frame ground for the headlights and gauge lights, as well as the front turn signals/running lights- do these go out as well? The tach and water temp. gauge also share the ground - what about these?
If these other components also fail to operate when the headlight goes out, I'd locate that grounding point, by following back the black wire.
There also appears to be a jumper wire, just prior to the grounding point, that joins the collected ground wires together. Perhaps one of the connections is wonky, or the wire itself is frayed.
Cheers!
 
Had a similar issue on a '96 I was working on, cleaned and di-electric greased the connections behind the left side steering neck cover and the problem was eliminated....everything looked great except one connection (believe it was in a green connector) which had some corrosion.
 
What is confusing me is when I look at the 85 US diagram there is a blue wire that looks common that is the only one that could be causing the problem. The thing is the way that blue wire connects is different on almost every diagram. It's like the diagrams are full of mistakes.
 
What is confusing me is when I look at the 85 US diagram there is a blue wire that looks common that is the only one that could be causing the problem. The thing is the way that blue wire connects is different on almost every diagram. It's like the diagrams are full of mistakes.

Yes the blue (power) wire is common to the gauge, speedometer lights, front running lights and taillight - but not the headlight. So unless there are two problems, the headlight and gauge lights should not fail at the same time.
No chance that the wiring was altered by a previous owner?
Did you check all the connections for all the various lights, any that may be put under strain when the handlebars are turned? Also check the infamous 3-wire connector , behind the headstock framing, that connects the ignition switch. The blue supply wire to all the above lights(except the headlight) is integral to this connector.
Cheers!
 
It looks like it runs from the gauge lights to the dimmer switch and then powers the headlight.
 
It looks like it runs from the gauge lights to the dimmer switch and then powers the headlight.

Whoa! If that's the case, your wiring has been severely F***ed with. Excuse my typed language. The power wire to the dimmer switch is blue/black, and originates at the starter switch. The starter switch is powered by a red/yellow wire originating from the dedicated 15 amp headlight fuse.
The above applies to all model years.
 
My apologies!:bang head:
I checked the wiring diagram on Sean's site. It differs from the Clymer manual diagram for your model year. Yes indeed, the blue/black wire does supply power to the gauge lights, and to the dimmer switch (then to the headlight)
Therefore there is a reason why your gauge lights and headlight would fail at the same time! I'd suspect the starter switch, since the blue/black originates there. It's only energized when the switch is in the "off" position (when cranking the bike the headlight is off, easing the load on the battery).
The contacts in the switch could be corroded. Also check the headlight fuse contacts, and the fuse itself. This is the source of power (via the red/yellow wire) to the starter switch.
Cheers!
 
Don't forget that sometime the starter button sticks a little bit and will cause the lights to go out. Some guys get away with spraying a little WD-40 in there and working the switch back and forth.
 

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