Author Topic: Dramatic Fuze Blow - V7 (Read 5030 times)

sign216 · « **on:** August 14, 2019, 04:09:06 PM »

Question: When a fuse blows completely, dramatically, totally, do you replace it w a higher or lower amp? Assuming you can't find the issue and everything seems fine now.

I added a "status interuptus" circuit to my V7 years ago. Today I found that the fuse for that circuit was spectacularly blown. The bike has a Li-ion battery and several (3 or 4) added circuits for gps, cigarette lighter, aux power, etc. I thought I shielded the positive contacts, but in a bike it's easy for things to slip, so I'm guessing a neg contact must have reached a pos contact. Now, everything looks good.

I replaced the blown 15 amp fuse w a 10 amp fuse because I didn't have any 15s handy, although my notes say the startus interuptus circuit is good for 20 amp. The bike started and ran fine w the 10 amp fuse, although the fuse holder terminals are burnt too and need to be replaced.

Any pithy observations?

Joe

[/url]Circuit w fuse holder[/img]

[/url]Burnt fuse - 15 amp?[/img]

Fontain25 · « **Reply #1 on:** August 14, 2019, 04:45:58 PM »

You almost had a fire. Wouldn't replace with a larger amp fuse.

wirespokes · « **Reply #2 on:** August 14, 2019, 04:53:03 PM »

That's scary! How many devices does that fuse protect?

I'd want to make sure I'd found the smoking gun before calling that one a wrap! There is something very wrong somewhere downstream and next time might not turn out so well.

No, I wouldn't increase the fuse rating. Add another fuse panel and run it straight off the battery for those extra circuits. Are those extra circuits protected by the blown fuse?

Chuck in Indiana · « **Reply #3 on:** August 14, 2019, 05:06:09 PM »

I truly don't want to offend you, but I probably will. <shrug> I've seen neater wiring jobs.. no telling what might have touched something else..

Bud · « **Reply #4 on:** August 14, 2019, 07:29:20 PM »

It looks to me that that fuse overheated, probably because of a loose connection at the fuse holder. if a fuse is overloaded it will burn out the link inside the fuse.
Not sure how to post a picture but I just had a similar thing happen on my 1400 Touring. Factory fuse block with one 40 amp and one 30 amp fuse in a tiny 1x1x1.25" fuse block neatly seated in a rubber case. Got off the bike and had smoke coming from under the seat. Totally melted the 30 amp fuse and part of the fuse holder. My guess is that terminals got some corrosion build up that caused a bad connection that caused friction which caused a melt down.

malik · « **Reply #5 on:** August 14, 2019, 08:18:02 PM »

Lucky escape, Joe. What wirespokes says.

I've had fuses blow a couple of times. In both cases it was a broken wire shorting out. Fix the problem, replace the fuse. And check the fuse base, while you're there.

Mal

sign216 · « **Reply #6 on:** August 15, 2019, 08:01:18 AM »

Yep, I've got to consolidate the wiring and tidy the misc. circuits up. Replace the fuse holder too.

The blown fuse has only one duty; it covers the direct line from the battery to the "startus interuptus" relay. It could have blown because the starter or solenoid had an abnormally high draw, but I suspect one of the other errant wires shorted out to it, causing the blow.

Joe

wirespokes · « **Reply #7 on:** August 15, 2019, 12:14:43 PM »

I don't know what Roy suggests, but considering the fuse is protecting the new solenoid circuit, and that only, I'm thinking 15 amps isn't enough. Quite possibly it melted due to the amount of current flowing through it. Since Roy says the circuit can draw 30 amps for a short period (milliseconds) it's probably a good idea using a 20 or 30 amp fuse. If it takes longer than a moment to start the engine, things will start heating up.

Chuck in Indiana · « **Reply #8 on:** August 15, 2019, 12:38:23 PM »

Years ago, I had the fuse blow when the starter solenoid hung up. Mark at MG Classics had a 5 gallon bucket of starters with either bad solenoids or dropped magnets and told me to find a good one. Did that, a practically new one with bad magnets and swapped solenoids. KR says a 15 amp fuse is adequate when everything is working ok.

malik · « **Reply #9 on:** August 15, 2019, 02:19:44 PM »

That makes sense, at least to me i(in my ignorance, it seems logical). A crossed wire usually seems to blow the fuse cleanly, but Joe's fuse was melted.

Kiwi Dave · « **Reply #10 on:** August 15, 2019, 03:42:19 PM »

I'm thinking that it wasn't a short circuit that blew the fuse. Rather, it was excessive current over a reasonably long period that allowed the fuse to heat up for quite some time before it decided to blow. Most likely, this heat was caused by a dirty fuse holder that created resistance (resistance x current²) that eventually caused it to blow.

Replacing the fuse holder (and other tidy up) is the wise thing to do.

sign216 · « **Reply #11 on:** August 15, 2019, 04:44:54 PM »

Quote from: Kiwi Dave on August 15, 2019, 03:42:19 PM

I'm thinking that it wasn't a short circuit that blew the fuse. Rather, it was excessive current over a reasonably long period that allowed the fuse to heat up for quite some time before it decided to blow. Most likely, this heat was caused by a dirty fuse holder that created resistance (resistance x current²) that eventually caused it to blow.

Replacing the fuse holder (and other tidy up) is the wise thing to do.

The fuse holder does look burnt, but not nearly as bad as the totally done fuse itself. I'll be replacing the fuse holder as well as cleaning up the wiring. We will see.

So here's another question. When a fuse is totally burnt like like this, is it due to a sudden rush of overwhelming current, or a gradual overheating?

Bud · « **Reply #12 on:** August 15, 2019, 08:15:06 PM »

If there is over current, more than the fuse is rated at, it will blow the fuse link. If there is a bad connection or constant load close to the fuse rating it can cause heat.
Circuit breakers used mostly for industrial purposes come in different delay times. In other words they are designed to take more current than the circuit breaker is rated for for a predetermined time. I'm not sure about the type of fuses we are using in this case but I would think they would immediately blow above their rating.
As mentioned above my 1400 Touring just had a melt down. I was unable to get the OEM block so I installed two fuse holders rated at 40 amps. You have to use a holder that can handle the load you are going to put through it.
Just got back from a test ride and checked the fuse holders with my hand. I don't have anything to compare it to but they felt a little warmer than I like but no melting! The fuse holders are rated by the wire size but the contact area where the fuse plugs in is the same for a 15 amp as it is for a 40 amp.

Chuck in Indiana · « **Reply #13 on:** August 16, 2019, 06:54:26 AM »

The V11 Sports have a habit of doing that to their 30 amp fuse on the charging circuit. It's generally just from a loose/corroded fuse holder. Docc put a 30 amp aircraft

circuit breaker on his.

Bud · « **Reply #14 on:** August 16, 2019, 05:54:19 PM »

I may have to look into that if this gets warmer than I like.

Kiwi Dave · « **Reply #15 on:** August 16, 2019, 06:41:12 PM »

You could try cleaning up the surfaces of the fuse blades with fine emery paper to increase the conduction.

Perhaps also apply Deoxit-D to both surfaces to further reduce any resistance. You should be able to see any improvement with a quality DVM on its low resistance range.

Kiwi_Roy · « **Reply #16 on:** August 16, 2019, 07:37:11 PM »

The melting is caused by a bad contact in the fuse holder even 10 Amps can cause a lot of heat across a resistance.

Just buy a new fuse holder and replace the fuse also
I would recommend a 15 Amp fuse with the direct feed the current will spike around 40 Amps but just for a few milliseconds.
Scrape the leads and terminal posts clean and apply Vaseline.

sign216 · « **Reply #17 on:** August 17, 2019, 05:58:09 AM »

The fuse holder was slightly burnt, but nearly as bad the demolished fuse. This is understandable, as the fuse is/was designed to "fail" when things got tough. Still, I'm surprised that the minor burn at the fuse holder caused the fuse to disintegrate.

I'll be replacing the fuse holder this weekend, assuming the wife doesn't grab me w some "essential" chore.

Joe

sign216 · « **Reply #18 on:** August 17, 2019, 04:37:06 PM »

Attached is a photo of the fuse holder. Some think that resistance in the holder may have caused the fuse to blow. You can see that the holder is burnt, but now it's a chicken-egg thing. Whether the blown fuse burnt the holder, or the bad holder caused the fuse to blow. Regardless, I changed everything and we'll see what comes. Joe

[/url]fuse holder - slightly burnt [/img]

Chuck in Indiana · « **Reply #19 on:** August 17, 2019, 07:16:55 PM »

I'm betting the fuse holder was corroded or not tightly holding the fuse. I'm calling that the chicken.

Bud · « **Reply #20 on:** August 17, 2019, 07:51:22 PM »

Quote from: Chuck in Indiana on August 17, 2019, 07:16:55 PM

I'm betting the fuse holder was corroded or not tightly holding the fuse. I'm calling that the chicken.

I second and third that!

lucian · « **Reply #21 on:** August 17, 2019, 07:53:42 PM »

Looks like arcing in the fuse holder Joe. Used to see it often on golf carts . The fuse wouldn't blow as there was no short , just repetitive arcing when there was a load. As the arcing progresses ,the arc gap becomes bigger and the amp draw increases and becomes exponentially hotter, kind of a run away snowball. glad you got it sorted out,

Kiwi_Roy · « **Reply #22 on:** August 17, 2019, 08:41:39 PM »

Quote from: Bud on August 17, 2019, 07:51:22 PM

I second and third that!

I'm not even going to answer that, we told you it's caused by heat due to resistance.

sign216 · « **Reply #23 on:** August 17, 2019, 09:10:24 PM »

Well everyone has spoken. I changed the fuse holder, inserted the new fuze w conductive grease, and I hope that solves the problem.
The last arrangement lasted several years. I'll keep a closer eye on this one.
Thank you all for letting me know your wisdom.

Joe

nc43bsa · « **Reply #24 on:** August 20, 2019, 04:27:44 PM »

The ground bar in the center of the first picture looks gnarly, also. I hope it actually is used as a grounding point. It looks like there is a red wire attached.

sign216 · « **Reply #25 on:** August 20, 2019, 08:19:03 PM »

Quote from: nc43bsa on August 20, 2019, 04:27:44 PM

The ground bar in the center of the first picture looks gnarly, also. I hope it actually is used as a grounding point. It looks like there is a red wire attached.

Are you talking about the ground bar (center-ish in the photo) or the fused accessory grid in the upper left? The ground bar only has ground wires, and the accessory grid (now removed) was formerly used to power some defunct circuits. The are no longer in use, and that whole circuit + relay is gone.

Joe

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Author Topic: Dramatic Fuze Blow - V7 (Read 5030 times)