Replace Circuit Breaker with 40 amp Fuse

[Tsani]

Wiring for automotive use s rated differently. Not the same as a house, etc. Even Marine wiring is rated differently. Think in terms of watts or power that a wire can handle and things change accordanly. Here is a site you can check to give you an idea for your bikes:
http://www.tessco.com/yts/industry/products/itm/automotive/get_wired.html

Another thing to keep in mind with your bikes is it is about the total wiring length, supply side, load then ground. All comes into play.

[Bagger]

Who has a source or link to the fuse holders KENR used in post #9.

[Ken R]

Who has a source or link to the fuse holders KENR used in post #9.

I got mine down the street at Pep Boys.  I think AutoZone has 'em, too.   They're made by Littelfuse.

This may be them

[glens]

If the fuse (or breaker) blows, the motor is supposed to die.

I missed that part in the instructions.

When the motor dies, the alternator quits producing voltage.  This theory is supposed to protect your motorcycle's wiring from burning.  Fuse blows, disconnecting the battery, motor dies, no more current.

Sounds good if true.  Are you sure that's what's supposed to happen if you lose a maxifuse/breaker during normal operation?

What it, though, you're at 80 mph and you leave the clutch out?  Motor dies, but is still spinning with the alternator/regulator still producing electrical current at up to 45 amps.  The second fuse I installed is to further protect the motorcycle's wiring.  One should blow.  Then the other one if the over-current problem is still there.

I'll agree with that.  After all, I guess we're just assuming the voltage regulator has or has-not any sort of overcurrent protection within itself?

It should also be noted that HD's fuse (or circuit breaker) breaks the wire between the battery and motorcycle's wiring, leaving the charging system still connected.  The shop manual states that one should never disconnect the battery while the engine is running, else damage to electrical components could occur.

That's still the "current" connection scheme according to the '09 service and electrical PDFs I just electronically searched through.  Warnings or statements like you say just there, however, are not present in either of them.

Actually that rather surprised me because the danger in doing that (pulling a battery lead from a running bike) is that in the event the battery was heavily charging, there would (historically?) be a fair amount of hydrogen gas present, which a spark could ignite.  Right?

My circuit breaker tripped, a voltage spike hit all of the electronic devices.  My breaker tripped and reset several times in the matter of a few seconds.  I was at 50 mph with the clutch out.  Each time it tripped, it produced or had the potential to produce voltage spikes as the battery was disconnected and reconnected each time.  The result was $1,200 in damage to electrical components.  TSSM, Speedo, Tach, Radio, and a few other components were victims of the voltage spike.

I'm sorry that happened to you.  So you've sussed this out and concluded that putting an extra maxifuse in the charging circuit would prevent it from recurring. 

How about instead of two fuses, if the breaker were left in place in conjunction with an additional charging-feed fuse?  Would that combination have availed you any better protection than what you had?

Like I suggested above, I'd sure think the regulator had some internal means of overcurrent protection/limiting.  I submit that what'd happened to you was solely the fault of the breaker.  Voltage spikes from the charging system loading/unloading?  Yeah, perhaps some of that went on, but with a fuse in place of the breaker, the circuit wouldn't re-close.  I wonder if the breaker contacts repeatedly arcing might've introduced an unfavorable "rasp" to the power and that's what took out your electronics.

By the way, what was the reason the breaker tripped?  Had you a short in the loom somewhere or was it just a weak unit?  Was the battery shorting internally causing the charging circuit to overload the breaker?  Which kind of brings up another thought.  If you had a short somewhere causing this much breaker action, wouldn't the short have pretty much taken care of the spikes for you (if not on the battery side of the breaker)?

[smoserx1]

I still don't understand why the engine would die if the breaker or maxi fuse blew with the stock wiring configuration.  The output wire from the regulator essentially bypasses the breaker/fuse altogether and attaches to the ignition switch feed (the B+ wire?) downstream of the breaker/fuse.  It looks like the electrical system of the bike would continue to receive power from the charging system, even if the breaker/fuse failed.  All that does is disconnect the battery.  Of course the current with no battery present would have a ripple waveform to it, and you would not have the battery present to help smooth the ripple.  I have read the battery helps smooth the ripple.

The paper Max pointed us to earlier in this thread explained very well why the spike occurs when the battery is disconnected with the engine running.  The paper refers to that scenario as a "load dump."  Here it is again if anybody missed it:

http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

[glens]

But that text is in terms of field excitation current which we don't have.

[Ken R]

Glens, I did finally find out why the circuit breaker was tripping . . . .and it wasn't because of an over-current condition.  It was the crimp connector on the little 12 ga wire that attaches to the output side of the breaker.  The crimp connector developed a slight electrical resistance that disipated power in the form of heat.  Being connected directly to the circuit breaker, the heat was conducted directly into the circuit breaker. 

After all the repairs to fix the problem, I was not happy at all.  I'd treated the symptoms but had done nothing about the root cause of the failure.  Fretted over it for weeks.  I remember touching the circuit breaker and it burned my finger.  "Hmmmmmm,"  (right after "Ouch, that's really hot!")

I measured the circuit breaker temperature at almost 100C at times.  Thought it was coming from the engine and rear cylinder exhaust pipe.  The breaker would be very hot to the touch.  I tried a lot of things to thermally isolate the breaker from the frame.  Then, a little light bulb went off in my head.  Why is the circuit breaker the only thing in the area so hot?  The bulkhead between the exhaust and the breaker wasn't even as hot!

Sure enough, it was the crimp connection lug.  The circuit breaker de-rates to about half its stated value in such hot conditions.   Well, duh!

I think this is the original problem with the 40-amp breakers that HD had the call-back (or bulletin) all the time.  It wasn't that the breaker was of insufficient rating, but that it got hot from the crimp connector.  That's why so many that put the 50-amp breakers in still had intermittent tripping.  (like me).   

I was between Boulder and Denver.  Waited at a long stoplight with brakes on, then accelerated away and got almost to the 60mph speed limit.  Then, everything went dead and the motorcycle began to slow with the clutch out.  Before I could do anything, it came back alive.  Did this 2 or 3 more times; never recovered from the last time.  Ended our cruising the mountains a little early.  Trailered back to Dallas and began to diagnose all the stuff that was damaged by what I assume were high voltage spikes each time the breaker let go. 

[cyrus]

Ken that makes alot of sense. Also you are right there should not need to be a recall for the 40 amp circuit breaker because the alternator is feeding the bike through the load side of the breaker, therefore very little current should be flowing through the CB. The only current flowing through it at say highway speed would be the small current back feeding to the battery to keep it "topped or charged" up. And at idle the small supplementary current that the accesories need that the alternator may not be able to keep up with. Still this is very little current flowing through the CB in either direction. So why the recall? Bad connectors?

[02ultrarider]

I had the breaker recall done, left on a trip, rode 11.3 miles bike shut down, fired up rode all day no problem, next morning, 11.3 miles, shuts down again. stopped at a dealer in Peoria, they put in another breaker, and thats all they could do since it was not tripping. next morning, 11.3 miles again,, poof died again, and shorted out the radio. got to another dealer in Iowa. they tried a new breaker, mech rode it the next morning,,, yep 11.3 miles and poof. they had it in the shop 3 days. wife got fed up and called harley. they told the dealer to recrimp all the heavy wires around the battery box. got the radio replaced. and we were on our way again. weird huh.

[Dagwood]

I have a '99 Ultra that I converted to the newer style 3 phase charging system used since 2006.  I'm thinking of replacing my circuit breaker with a maxi fuse.  Would the dual maxi fuse setup in this thread be of any value on a 3 phase system or does the type of regulator used on a 3 phase system eliminate the need for something like this?

[Admiral Akbar]

Nope, Nope,
Max

[Dagwood]

A double nope?  It would be of no use on one hand, and the 3 phase regulator doesn't eliminate the need for something like this?  Does that mean this circuitry is flawed to begin with and of no real benefit?

[Admiral Akbar]

A double nope?  It would be of no use on one hand, and the 3 phase regulator doesn't eliminate the need for something like this?  Does that mean this circuitry is flawed to begin with and of no real benefit?

It depends on now many lights you plan on running..    The 3 phase should be more reliable.. also..(by design)
Max