Uh - OH, extra wire left over

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I finished installing a new battery and have a new unattached wire. Of course I didn't take a PICTURE before I started.
Can anyone tell me to what this is suppsed to attach? BTW, 15A fuse inside the dongle. ALSO, it starts...

extra.wire.JPG
 
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patdebtim
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I attached it to each battery post.....then the bike will not crank over, so......
 

Mark

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DOH!
I think you're going to have to follow the wire to figure out what it connects too!
 

DJDixon

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It looks like an accessory wire, note the in-line fuse. It should go to a power source (the 12 volt positive or "Red" side of the battery). If it is to an alarm, it may prevent the starting of the bike. As Mark said, time to trace out what it is powering...
 

ST Gui

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Whatever it's for it's almost certainly to be connected to the positive terminal. I don't think it's common to fuse the negative side of the battery though at least one person here has mentioned it. Pull the fuse to see if it's good.

Do you have any add-on bits like a power port or heated gear (though 15A might be more than enough for heated gear)? It could be just an SAE pigtail for charging or a 12V compressor etc.
 
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I don't think it's common to fuse the negative side of the battery though at least one person here has mentioned it.
The failure mode the fuse is there to protect is an unintended short to ground somewhere in the circuit before the load, where the current flow will only be restricted by the resistance of the wire, not the load resistance. Typical scenario might be a wire chafing and shorting out on the frame. The closer to the 12v source you place the fuse, the better chance you have of blowing the fuse prior to melting any wires, because if the fuse is downstream of the short, its useless.

Having the fuse anywhere in the path from hot to ground, so it will blow when something changes in the load resistance is technically valid. But, if the load resistance has changed, something has probably already failed and the fuse is just protecting the wires at that point anyway, so moving the fuse upstream as close as possible to the 12v source still makes the most sense.
 
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It is conventional to fuse as close as reasonable to the pos(+) post. Just about all the known world does it this way- I think it's called "conventional wisdom". And seems reasonable if you don't look too closely. It's built on an misconception. In a d.c. circuit current actually flows from neg.(-) to pos.( +) So following your line of reasoning, it would make more sense to place a fuse close to the neg. post..... No? All my installations I've stuck with the known world and fused close to the + terminal. Simply because it makes it easter for anyone else to trouble shoot an electrical issue.
 
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Blrfl

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It is conventional to fuse as close as reasonable to the pos(+) post.
Not only is it conventional, it's the safe thing to do. The fuse goes as close to the non-ground terminal (positive on a negative-ground system) as possible so any short to ground will blow it out. If you put the fuse on the opposite terminal, electrons will flow unabated from the point of the short to the positive terminal. That's what starts fires, or at least releases the smoke that makes electrical stuff work. :D

--Mark
 
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In a d.c. circuit current actually flows from neg.(-) to pos.( +) So following your line of reasoning, it would make more sense to place a fuse close to the neg. post..... No?
Nope.

You are correct about the flow of electrons going from - to +, but the entire frame is used for negative ground. So any bare wire that touches the frame is creating a new (unintended) path for electron flow from the frame (-) to the battery (+) terminal. By placing the fuse as close as possible to the + terminal, if a wire chafes the frame somewhere in the path, then you're fairly sure the fuse will remain in that new current path to the battery (+) terminal.

Some applications have used positive ground in the past (didn't VW do this years ago??). In that case you'd want the fuse closer to the (-) terminal. Bottom line, put the fuse as close as possible to the non-ground terminal, then any unintentional grounding will include the fuse in the current flow path.
 
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Sorry I wasn't a clear as I could of been..the frame is a common junction point... It might help to think of the frame as nothing more than an extention of the neg battery post. A fuse inserted in the wire before its connection to the frame would work for fused protection .
 
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Sorry I wasn't a clear as I could of been..the frame is a common junction point... It might help to think of the frame as nothing more than an extention of the neg battery post. A fuse inserted in the wire before its connection to the frame would work for fused protection .
It is generally preferred to have nothing but a large gauge short wire between the ground plane and battery terminal so they are as close as possible in voltage potential. Adding a fuse into that path will create a voltage drop and cause the system ground to float a bit relative to the battery ground. You still get the voltage drop by putting the fuse on the other end of the circuit, but all parallel paths see the same ground voltage, and increasing the current flow doesn't cause the system ground to float even higher. Putting the fuse where you suggest would create a voltage drop that increases as a function of current load, and ground float would vary based on current draw.

Also, because its a common point, you couldn't assign different fuse ratings to different circuits, you'd only be able to put a main fuse there because every load would pass current through that same wire.
 
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Did you remove any bolts other than ones that are necessary to change out the battery? If not, that terminal goes to the (+) side of the battery.
The fact that the bike will not turn over with this wire attached has me scratching my head. Did you check the battery and see if it is indeed good? I have got bad ones right out of the box before. Are your connections tight?

Follow the wire to where it leads. I would suspect it goes to some sort of alarm or is the #30 terminal on a relay somewhere. I am assuming you did not install whatever this wire goes to.
 
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It is always a good idea to know what any given fuse protects - if only to save time later trouble shooting electrical gremlins. I'm firmly in the 'follow the wire' and label it so you know what it controls camp.
 
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Whatever it is it appears aftermarket. Do you have a heated seat or power ports anywhere?
As Mr. Blrfl mentioned if it's fused it's + not ground.

I guess the question is what farkle isn't working?
 
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