Wiring in a fuse.

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Captain80
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Wiring in a fuse.

#1

Post by Captain80 »

Hey guys, just finishing up my1960 FLH. Does anyone know where to wire in a fuse, and what size fuse to use? Just in case I screwed something up in the wiring , which is probably the case. Wouldn't want my new pan to end up in flames! Can't believe the factory didn't put something in the harness !
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Re: Wiring in a fuse.

#2

Post by awander »

A 20A fuse will work, and you can wire it up directly from battery minus to the frame ground point(inline with what is already there)
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Re: Wiring in a fuse.

#3

Post by Captain80 »

Thanks Andy
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Re: Wiring in a fuse.

#4

Post by Scrap »

I have noticed that in most posts regarding fuse placement, it is recommended that it be placed on the ground side of the battery. In high voltage applications, a blown fuse on the ground will leave the device dead, but if someone came in contact with the device the current could flow through the person to ground as the hot side is still connected to the power source. That's why the hot side is always fused. Is there a good reason to fuse the ground on a bike?
Thanks
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Re: Wiring in a fuse.

#5

Post by awander »

Well, the reason I suggested fusing the negative (ground) side is that I think it's more likely that an old bike, especially a non-stock one, will have only a single ground wire to the battery negative, while there may be more than one wire running to the battery positive.

From what I have seen, someone adding a new electrical device on a bike is likely to have added a separate new "positive" wire for that circuit to the positive terminal of the battery, while just picking up the ground from the bike frame (no new ground wire attached to battery).

It's just easier to fuse the single wire, rather than having to find a way to bundle multiple "hot" wires at the battery to go through a single fuse.

This, of course, only applies to bikes like ours that have negative-ground electrical systems. Many older cars and bikes had positive-ground systems.



Also, of course, what you wrote about high-voltage system is only valid if the system has the negative side grounded. With a positive-ground system, it would be exactly the opposite; the negative side would need to be fused for safety purposes.

I am not familiar with any high-voltage DC systems, except in theory. I know that some lower-voltage (48V) systems for telephone systems and the like had a positive ground.



Just curious, what are the high-voltage DC systems that you have used? I know a lot of things seem to be moving toward DC, there are even some high-voltage DC transmission lines these days.....
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Re: Wiring in a fuse.

#6

Post by awander »

Scrap, I just realized that you may have been talking about high-voltage AC(not DC) systems, as you used the terms "hot" and "ground", and not "plus" and "minus".
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Re: Wiring in a fuse.

#7

Post by Scrap »

Andy,
Thanks for the explanation, makes perfect sense, and I don't believe I've ever been near a high voltage DC anything. A DC welder?
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Re: Wiring in a fuse.

#8

Post by Wrong Road »

The electrons travel from negative (ground) terminal through the load. If you fuse at the negative terminal, the current will be stopped before it overloads the circuit. If you fuse on the positive side, there is a somewhat greater chance that the load could be damaged by too much current.
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Re: Wiring in a fuse.

#9

Post by awander »

Wrong Road wrote:The electrons travel from negative (ground) terminal through the load. If you fuse at the negative terminal, the current will be stopped before it overloads the circuit. If you fuse on the positive side, there is a somewhat greater chance that the load could be damaged by too much current.
Sorry man, but the electrons won't flow at all, if the circuit gets broken anywhere.
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Re: Wiring in a fuse.

#10

Post by 1962FLH »

I prefer using a 15Amp circuit breaker rather than a onetime fuse. I put this on the positive post of the battery, not that it matters because it don’t. Any type of protection you can use is better than none.
John
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Re: Wiring in a fuse.

#11

Post by cdndewey »

I'm partial to fusing the negative side. I learned many years ago in my mechanics course that when pulling or installing a battery, the negative is first off and last on.
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Re: Wiring in a fuse.

#12

Post by awander »

Theoretically, it shouldn;t matter which side of the battery gets disconnected first.

In the real world, if you disconnect the positive side(in a negative-grounded vehicle) there is a risk of shorting out the wrench or other tool to chassis ground, which is still connected to the negative of the battery. This makes for an interesting moment or two.

If you disconnect the negative first(while the positive side is still connected), shorting your tool to ground will do nothing, as negative is already tied to chassis ground.

And, of course, once the negative side is disconnected, shorting the positive side of the battery to the chassis ground will also do nothing.
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Re: Wiring in a fuse.

#13

Post by cdndewey »

awander wrote:Theoretically, it shouldn;t matter which side of the battery gets disconnected first.

In the real world, if you disconnect the positive side(in a negative-grounded vehicle) there is a risk of shorting out the wrench or other tool to chassis ground, which is still connected to the negative of the battery. This makes for an interesting moment or two.

If you disconnect the negative first(while the positive side is still connected), shorting your tool to ground will do nothing, as negative is already tied to chassis ground.

And, of course, once the negative side is disconnected, shorting the positive side of the battery to the chassis ground will also do nothing.

I was taught that removing the negative first reduced the chance of sparking and causing a battery explosion. The same holds true for boosting a dead battery. The negative of the bad battery got connected last and removed first.

Having had a battery explode in my face in 72 before learning the proper procedure, is still quite burned into my memory.
Last edited by cdndewey on Tue Jul 05, 2016 6:47 pm, edited 1 time in total.
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Re: Wiring in a fuse.

#14

Post by awander »

cdndewey wrote:
awander wrote:Theoretically, it shouldn;t matter which side of the battery gets disconnected first.

In the real world, if you disconnect the positive side(in a negative-grounded vehicle) there is a risk of shorting out the wrench or other tool to chassis ground, which is still connected to the negative of the battery. This makes for an interesting moment or two.

If you disconnect the negative first(while the positive side is still connected), shorting your tool to ground will do nothing, as negative is already tied to chassis ground.

And, of course, once the negative side is disconnected, shorting the positive side of the battery to the chassis ground will also do nothing.

I was taught that removing the negative first reduced the chance of sparking and causing a battery explosion. The same holds true for boosting a dead battery. The negative of the good battery got connected last and removed first.

Having had a battery explode in my face in 72 before learning the proper procedure, is still quite burned into my memory.
Exactly
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Re: Wiring in a fuse.

#15

Post by 1962FLH »

Where is or should the fuse go to protect the Pan is one topic. To me disconnecting or jumping a battery the correct way for personal protection is really off topic here but well worth the mention. Having said that we are in total agreement as the motor does not care and will preform the same regardless where the fuse is placed; or even if you don't have a fuse at all.

Thanks.

John
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