What did you do to your Royal Enfield today?

[gremlin]

Today, I changed the main fuse..........
................I suspect that after over a year and a half of riding, that fuse just got tired of carrying the power load...........

Um, you know better than that.

repeat after me ---  " The purpose of a fuse is to protect wire insulation from catching fire "

[Jack Leis]

Um, you know better than that.

repeat after me ---  " The purpose of a fuse is to protect wire insulation from catching fire "

+1!!!

[LarsBloodbeard]

+2

A fuse isn't going to just get tired and "wear out."

[mattsz]

Could the same vibrations that loosen our nuts and chafe our wires weaken a fuse?

[barenekd]

Could the same vibrations that loosen our nuts and chafe our wires weaken a fuse?

yes. You'll find out if that's what it is as soon as you stick a new one in there!
Bare

[LarsBloodbeard]

Could the same vibrations that loosen our nuts and chafe our wires weaken a fuse?

By way of a loose electrical connection.

[Jack Leis]

It takes a short or a load surpassing the fuse rating to blow one.

[mattsz]

but it's a metal filament - can't it be physically broken without passing too much current through it - like a lightbulb?

[Jack Leis]

A 15 or 20 amp fuse is a lot less prone to break from vibration then a lightbulb filament . Try again Mattsz  .

[mattsz]

A 15 or 20 amp fuse is a lot less prone to break from vibration then a lightbulb filament . Try again Mattsz  .

I'll gladly give you "a lot less prone", Jack!  But is it impossible?  I know these "u-shaped" plug-in fuses have a very different shape than the older tubular "straight-filament" style ones. The former must be sturdier, I would suppose.  I guess what I'm really wondering is, what are the odds that a blown fuse could be broken due to too much vibration rather than melted due to too much current.

I'm not trying to win an argument here - I really don't know!  Moving on...

[LarsBloodbeard]

No.  Jack is spot on.  With the kind of vibration you're talking about, it would break many other things on your bike first.  Also the former are not sturdier, as the element does not have much room to expand and contract, which is why modern fuses have that bend in them.

Since it didn't pop on the road, chances are it's a poor connection, not a short.  Something as simple as a loose or fouled battery connection can blow a fuse.  A poor connection increases resistance which decreases voltage, and therefore current increases to make up for it.  Basically it's like running 20ga wire where you should have 4ga.  Anyone who has used the wrong wire like that knows the wire will get super hot.  This scenario with a fuse in line will blow if the current increases to exceed the rating.

[Jack Leis]

Mattsz, I don't claim to know everything. I am a retired licensed electrical contractor and a certified , licensed electrician. Thru all the years Ive wired up about everything but lightning. I HAVE NEVER SEEN A BLOWN FUSE FROM VIBRATION. Now that's NOT say it couldn't happen but I really f#$kn doubt it. Fuses blow for a reason. Usually some pissed off electrons , not vibration. Regarding the ODDS mattsz ? Only the guy's in Vegas can answer that one !

[Arizoni]

I don't know for a fact but being a long thin piece of flattened metal that it is could conceivably allow it to vibrate at some frequency and become weakened by metal fatigue.

With the very poor quality of the Indian made light bulbs that came on the bike as an example, nothing would surprise me.

I also notice that the flat "wire" has hundreds of little black specs or dots on it throughout its central area which don't exist at the ends.  I don't have a clue about whether this is some sort of calibration method used by the Indians, some sort of metal reaction to becoming hot from the current flow or just what it is.
I do know that I've never seen this sort of thing on a fuse made in the US.

Whatever the case may be, I now have over 80 miles of riding with the new fuse I got at the auto parts store installed and everything is working like it should.

If the old fuse blew because of a short I would think it would have resurfaced by now but I admit, you never know when it comes to those sneaky electrons. 

[Jack Leis]

Those sneaky electrons, the bastages that they are , always follow the path of least resistance. My riding buddy Bare had the same dilemma Jim. We are only dealing with 12 volt here and low amperage at that. If there were a short to the frame anywhere from poor insulation and vibration it might not always leave a blast mark on the location. The short could be very intermittent and cause the fusible material to anneal itself which would greatly lower the fuse ampacity. That being the case just a slight potential to ground could blow it. That's my take on what happened to you and bare's fuses. IMHO, no matter how bad we want to blame the blown fuse, there still had to be a short, no matter how small, that caused it to blow.

[Jack Leis]

While I'm thinking of it, BUSS makes some very good quality fuses that can be used on our bikes. But, I wouldn't be surprised if they are now made in India