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Main 30A fuse blowing, possible culprits?

7K views 18 replies 10 participants last post by  giancarlopetrini 
#1 ·
So, my bike is obviously still in the shakedown phase of it's post-build life. I've finally solved all of the leaks and drips and other mechanical problems, so it's only natural that an electrical problem should rear its head.

I've blown 3 30 amp main fuses in the last week, for no apparent reason. I've inspected every wire I can find, but I can't seem to locate any stripped insulation or obvious shorts... so I've got a few questions.

First: what systems are tied into that main fuse? Obviously the whole bike's electrical supply is controlled by that fuse, but if I were having a short in some subsystem wouldn't the associated fuse (fuel, lighting, etc) blow instead?


I've narrowed down what causes the fuse to blow, though I can't seem to replicate it when I've got the bike opened up for inspection.

Of the three fuses I've blown, the first blew while parking the bike. I'd ridden up on the sidewalk and turned the bike off, then I maneuvered it into a tight spot up against a wall. When I came back to the bike a few hours later, she was dead, and the main fuse was blown. It seems like the fuse blew while the bike was turned off, or at least not running. The next two times (both last night), the fuse blew during low-speed (city street) left hand turns. This leads me to suspect a few things. First, given that the bike seems to be able to lean left with no problems and go over gnarly potholes/bumps just fine without blowing a fuse, I think the short is somewhere in the bundle of wires that goes to the front controls of the bike and the ignition switch. Something about turning the bars to the left? Second, if the fuse blew while the bike was off, while I was maneuvering it into that spot (and turning the bars back and forth quite a bit to get it in), the short must be on some circuit that's hot when the bike isn't keyed to the "on" position.

So my second question: what systems in that area of the bike can blow the main fuse, and are capable of causing a short when the ignition is turned to the "off" position? The only thing I can think of, possibly, is the ignition switch harness itself.

What do you guys think? Any suggestions?
 
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#2 ·
man, you got a bad ground or a dead short somewhere..
stuffed anything in the tail under the seat??
mine did the same thing as i removed my subway sammich the night before.. i come out the next morning get all packed up lock the cabin, uhh, keys are on my bed, i can see them... anyway, finally get my key, NO START!!! that's how i know...
 
#3 ·
Wow, great description of your problem! You've got things narrowed down pretty well. Hard shorts are easy, but intermittent like this can be a PITA. To restate, you said:
1) only main fuse blows, no others,
2) seems to fail when making left turns/moving handlebars, and
3) seems to have failed with the ignition OFF.

That narrows things down considerably. It looks like you problem can be isolated to:
1) only circuits BEFORE the ignition switch.
2) none of the sub circuits (lights, fuel, fan, ignition, etc...)
3) wires that get moved when you turn.

That all points to just the Black/Red wire from the main fuse that runs up to the ignition switch. There isn't much else that fits all you symptoms.

You might try to make it fail by moving the handle bars back and forth a lot while monitoring the fuse. If you can get it into a mode where you can repeatedly make it fail, then you're in good shape. Do this with the ignition in the OFF position so you can make sure that the problem is BEFORE the ignition switch.

I'd take a close look at the wire from the harness that go to the ignition switch, specifically the Black/Red. Maybe it got pinched by the triple tree? Also, it'd be a good idea to download the service manual which has the wiring diagram. Let me know if you need the link. Good luck, you'll find it!
 
#7 ·
Second, if the fuse blew while the bike was off, while I was maneuvering it into that spot (and turning the bars back and forth quite a bit to get it in), the short must be on some circuit that's hot when the bike isn't keyed to the "on" position.

So my second question: what systems in that area of the bike can blow the main fuse, and are capable of causing a short when the ignition is turned to the "off" position? The only thing I can think of, possibly, is the ignition switch harness itself.

You're right. If the switch is in the 'ON' position when the fuse blew, then you need to look also at the plate light, the running light. From the description though, I still think the problem is likely to be at the front of the bike, and like eisenfaust is suspecting, maybe related to the ignition switch wires.
 
#8 ·
I think I may have solved some of the problem, though I'm not sure. The easytaps that go to my sportVUE hud module were loose/unscrewed, and those are tapped into my license plate light. Not quite sure how those would short though.

I'm also running a blitz headlight, and the wiring for those is notoriously bad.

Like I said, I have no idea if the fuse failed while the bike was off, but I'm counting it as a possibility. I'll check the black/red wire and see what I get.
 
#9 ·
So no dice on the black and red wire; I can't get the main fuse to blow.

If it were something in the lighting, I'd suspect the headlights, but what would cause the short? The bulbs in this headlight are quite a bit lower wattage than the stock H4 bulbs, so I don't think its a current draw thing. I also didn't modify the harness at all, I just plugged the new headlight into the standard headlight plugs with spade connectors.
 
#10 ·
Please be careful, as your bike might be dangerous to ride the way it is. If it suddenly dies on you, especially while making a left hand turn across oncoming traffic, it could leave you a sitting duck.

One other thing that might help you isolate the problem, (if you can get it to occur), is to try to make it fail while in a dark quite place, like inside a garage at night. If you're blowing a 30amp fuse, you will definitely see a spark, and maybe hear it too. Good luck.
 
#12 ·
Please be careful, as your bike might be dangerous to ride the way it is. If it suddenly dies on you, especially while making a left hand turn across oncoming traffic, it could leave you a sitting duck.
Emergency lights, clutch in, coast to the side of the road.

Don't ask me how I know ;D

Mine turned out to be my taillights that I tapped for the relay I put in but forgot to tape up a "wrong wire" that I tapped into. It touched the subframe and poof. (yes, my subframe is missing some paint in areas close to this wire thanks to storing my OnGuard chain/lock there)
 
#14 ·
In order for one of these wires to blow a fuse they'd need to short to the frame or something like that, right?

IE, a turn signal wire isn't going to blow a fuse if it frayed inside its insulation and contacts its own ground, right?

I've got aftermarket signals and brake lights, but the wiring is all very neatly done, shrinkwrapped junctions, tapewrapped harness, etc. I've inspected everything and can't find any chafed wires, loose connectors, etc.

The only two odd things I found:

1) the easy-taps supplying power to my HUD transmitter were kind of loose. I removed them.

2) The one of the spade connectors into my headlight plugs was missing its insulation, but I can't think of anything it would have contacted to ground out and cause a blown fuse. I even tried touching it to the frame, etc... no dice, fuse wouldn't blow.


I'm going to put her back together and keep riding around the neighborhood, try to get the thign to blow again. Manual fiddling with components doesn't seem to be getting me anywhere. :(
 
#16 ·
riding last night my main 30amp fuse blew. i was riding, going through a nice rolling left hand curve. bike had not been having any other problems during the ride. just dead right then and there.

after reading through the thread, mine may have blown because of the plate light wire that is no longer being used because of my fender eliminator.
 
#17 ·
my fuse blew last week when i switched the key to the off position. I doubt it blew AFTER the "off" position. Did you turn the bike off and then try to switch it back on again right away? It didn't read that way in your initial post. I think you're looking in the right area, but I would rule out anything happening after the "off" position.
 
#18 ·
Guys I just figured out a big NO NO. Was riding along and my bike just quit I mean everything. Did the same thing almost 2 years ago about a block from my favorite local bikeshop.
They said it was R/R and advised it would be best to replace stator and R/R since it is a 1999 first Gen. Price was not bad and I love my bike so had the work done.
All was well till about 3 weeks ago and it did the same thing. Tested stator..good tested regulator slightly off but still ok.Had battery load tested...good. Found main fuse blown,Replaced it now I had lights and all electric working no starter. After about 3weeks of tests prayers say the dreaded green plug thread here. So all I did was spray a good amount of WD40 into my ing switch and baby is back. Now heres why this worked as I can only think of....A few month ago some bike were stolen in the area. I used to never lock my bars. Well I decided it might be a good idea. When I tried my ign switch wouldn't turn all the way to lock? So I used Graphite to lube the lock not thinking that Graphite conducts electricity. The green plug thread made me think Corrosion? Flushed wth WD and baby is back. Sorry about the long post but don't use graphite in your ign switch.
My prob solved hope it helps someone else....Peace Barry
 
#19 ·
Same thing happened to mine, ended up being a short. My the connector where the stator wires hit the the regulator wires was frayed ever so slightly. A single exposed wire tapped the frame and blew the main fuse. It took 3 times and the smell of the fried regulator for me to find that root cause. Took the opportunity to swap in a regulator from a CBR1000rr. Good luck to you!
 
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