blowing fuse help!

[Ronkom]

96 Cali 1100I, suddenly started blowing fuse for circuit connecting idiot lights, tach, charging system, headlights. Will sit & idle fine, blows w/in 50 feet driving away.
Been through all the checking of multiple wire connections on steering head, wire bundles etc. etc. Replaced 15 fuse w/a 5, checked, pulled & jiggled...STILL can't find short.
Question, is there a possibility of an  internal short in the regulator? In my experience the alternator either works or doesn't, correct? Any & all ideas appreciated.
ronkom

[john hooper]

 I had a similar  problem on my ev, turned out the wiring to one of the idiot bulbs had frayed  where it entered the instruments and was shorting out.

John

[John A]

Look especially under rear fender at wiring and at tail light assembly

[pehayes]

It sits at idle OK and  then blows when you move.
Try to sit at idle and then, without moving, rock the handlebar back and forth.
Try to sit at idle and shift in and out of gear without actually proceeding.
These might hint at further inspection.  Sure sounds like a chafing incident.

Patrick Hayes
Fremont CA

[wirespokes]

This is the problem with multiple circuits on one fuse. Which one is the culprit?

One of the tricks of trouble shooting is 'divide and conquer'. A lot of times, like now, locating the fault is part of the job. So divide the search zone and eliminate the areas that don't have the fault.

Wiring diagrams are like hieroglyphics, but once the symbols are understood, wa la - you understand Egyptian! So take a look at the diagram and figure out how to separate the circuits, narrowing the search area.

Or, there's the hit/miss method - try this, try that until hopefully the fault goes away.

The main problem with trouble shooting is it requires a bit of understanding of the system viewed. It requires rolling up your sleeves and figuring out how the damn thing works.

[Testarossa]

The other issue of course is whether anything has been added to the circuit by a previous owner, or the wiring rerouted. Are you certain that the wiring harness is 100% stock?

[nsmith]

My 2001 did same thing, wire for tach light found its way to the chrome cap that covers the tach guts..

[Ronkom]

Thanks for the replies so far......I have a 24" X 36" color blow-up of the wiring diagram taped up on the wall next to the bike, so I can trace what I can see of the circuits. Tank, side covers off, a bunch of cable ties cut off to pull loose the various bundles to see where the black-stripe-on-red-wire goes. The circuit does feed the brake light switches, but the only time those wires would be "hot" is when the brakes were activated, which rules out the wires under the fender to the tail lights. 
Up front, where the circuit exits after feeding all the dash lights a diode symbol is in the diagram. It is depicted so as to prevent current from flowing back from the microprocessor to the dash lights, does that make sense?
Still no answer to the possibility of a sporadic short hidden inside the regulator or the alternator, can anyone give me a yea or nay?
Ron

[Testarossa]

If the bike is charging normally it's not likely to be a short in the regulator/rectifier/alternator. Have you measured idle voltage to confirm that? Have you had the alternator cover off to see if anything is loose or burned?

[Ryan]

I hunted a short for hours on my Kawasaki. Turned out to be a bad bulb. Easy to check by removing them all, so I start there now when faced with a drain or short.

[Ronkom]

Bike would charge normally until the fuse blew, then no charging, no dash lights, tach drops to zero, no headlights.  Bike would continue  to run just fine....until the battery voltage got too low.  I may have to put it all back together & do some testing myself. Would a shorted bulb filament carry enough juice to blow a 15 amp fuse?
Ron

[wirespokes]

I'd think a direct short would blow the fuse.

Doesn't sound like the alternator is the problem. But I'm no expert with the newer alternators than the Bosch.

Is there no way to unplug the separate circuits from the fuse block? If there's no way to separate them at the fuse, then perhaps disconnect them at the receipt point? Like disconnect the hot lead at the gauges and see what happens.

[Kiwi_Roy]

If I were to take a guess it would be something downstream of the brake switch e.g. short in the stop light, you move off then apply the brake and the fuse blows.

An electricians trick is to replace the fuse with a bulb, for this case I would wire both filaments of a headlight bulb in parallel and wire them into the fuse socket. This setup provides enough current to operate all the circuit components but if you short it out the lamp just turns on flashing the bulb at full brightness so you get alerted but no fuses are harmed

e.g. (it turned on full when I touched the brake)

[wirespokes]

I'd forgotten about that one, Roy! Thanks for the reminder.

[Testarossa]

The single most vulnerable point for insulated wires is where the brake and tail light power passes thru the rear fender. So check the brake light circuit first.

[Sasquatch Jim]

Queer electrons blow fuses.

[Ronkom]

Final.......Front brake light switch was erratic (but never blew the fuse on the table). So replaced the bad switch, and the "lights" relay that the offending fuse  feeds. Check-recheck all plug connections, pull, jiggle, put miles on the bike. No more blown fuses. I have to call it "fixed" even though I didn't find a "smoking gun".
Thanks for the replies/suggestions.
Ron

[Chuck in Indiana]

Thanks for the update, Ron.

[80CX100]

Queer electrons blow fuses.

      If you keep throwing good lines like that out,,, the winter won't seem that long, 

      Kelly

[SIR REAL ED]

Thanks for the replies so far......I have a 24" X 36" color blow-up of the wiring diagram taped up on the wall next to the bike, so I can trace what I can see of the circuits. Tank, side covers off, a bunch of cable ties cut off to pull loose the various bundles to see where the black-stripe-on-red-wire goes. The circuit does feed the brake light switches, but the only time those wires would be "hot" is when the brakes were activated, which rules out the wires under the fender to the tail lights. 
Up front, where the circuit exits after feeding all the dash lights a diode symbol is in the diagram. It is depicted so as to prevent current from flowing back from the microprocessor to the dash lights, does that make sense?
Still no answer to the possibility of a sporadic short hidden inside the regulator or the alternator, can anyone give me a yea or nay?
Ron

All good advice so far.  Electrical shorts can be a bitch.  Some times profanity and alcohol help.

My 07 Nevada 750 might not have a damn thing in common, wiring wise, with your bike, but my bike was doing the same thing.  The previous owner has wired a couple cute little LED lights into the brake circuit.  Sure did look cute seeing those two little lights light up next to the brake light.  Just plain dumb luck that I happened to notice one had bit the dust and was not lighting, and taking down the instrument panel when either brake was applied by blowing the fuse.

I have no idea why the LED bought the farm when it did, but a side cutters quickly removed the unwanted wiring.  Unlit LED's still fill the holes.

So it might not hurt to look at the brake light system.  Maybe remove the brake light bulb and see if the fuse still blow.  Is it blowing when you hit the brake and put the bike in gear?