Funny fuse

tom3c75

tom3c75

Hero member
Location
Cape Town South Africa
Was out on my 3C today and stopped to admire the view.
When I tried to restart the bike the electrical system was stone dead.

First thing to check then were the fuses, and did indeed find that the 25Amp fuse had dislodged from its fitting in the original fuse box. Repositioned the fuse and all was well again.

However, about 50 kms later, while riding, the bike died on me.
So, back to the fuse box, and found that the one end of the fuse body had melted out of shape, causing a complete lack of contact. Fitted my spare 25A fuse and, once again, all was well.

The melted fuse was a recent replacement of the original 25A fuse, which had lasted 40 years, before the fuse body broke.

Could this be due simply to the poor quality of the new fuse body, or should I be looking for a deeper problem?

Tom
(Electrically challenged)
 

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According to Clem, those replacement fuses are crap.
Probably arcing due to loose fitting of the metal strip is the cause of your problem.

Paul
 
Hi Tom,
It could be the poor quality of the replacement fuse, but it looks like that (melted) end of the fuse has gotten fairly warm, but not enough to melt the fusible link.
I'd suggest, as a start, thoroughly cleaning/polishing the fuse box contacts and gently bending them in so that the new fuse is held tight between the ends.
Someone will, no doubt, be along shortly telling you to damn the torpedoes and fit blade fuses, instead. They keep telling me the same, but my originals are still doing what they should, and have been for nearly forty-five years.
 
OK.
Observations: My 25 Amp one (arrowed) has a significantly wider metal, fusible strip.
The Mercedes ones are definitely ceramic. I don't have a 25 Amp one, but it would be simple to transfuse (see what I did there) the metal strip onto one.Fuses 1 Arrowed.jpgFuses Mercedes.jpg
 
having the electrics getting to where you need it is so important, and has let me down a few times (once in Breganze) that I no longer trust the "tension" in a tiny piece of bent brass sheet to maintain the contact, blade fuses is the way to go, its modernisation for Christs sake, you wouldnt ride your bike using 1970's chains or tyres would you? they have come on so much, go modern and a problem gone, nothing lasts forever, least of all the tension in what started as a shit bit of cheap brass crap.

All this is exasperated by the quality of the torpedo fuses, the metal of the fuse is loose on the carrier (it wasnt in the past) , and a point loading at one end (the screw end of the fuse box) and a small circular contact at the tang end is very likley to be lower resistance than 25 amps, hence the build up of heat., resulting in, not a blown fuse, but an unplanned circuit break elsewhere. Its one of the cheapest upgrades to do on your Laverda, so why not! picture shows fuse box, costing about a fiver, with its clear cover removed, flag terminal one end, and straight the other.
CLEM
 

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I rummaged through my stock of spare fuses and managed to find a few ceramic ones, including one 25 amp.
And I'll use the idea of switching the metal strip in order to make a couple more ceramic 25A's.

Clem, can't argue with your logic. I've upgraded the ignition and alternator with a Redax/Saches unit, so I can't use originality as an excuse not to fit a more modern fuse system. In the meantime I'll use the ceramic replacements, and also clean and tension the holding clips as has been suggested.

Thanks to all for the feedback.
 
Hi Clem, Hear what you say about 'Blade Fuses' but nearly every Zane I've worked on as to have a number of the blade fuses replaced because they have corroded into a white powder.! May be a combination of too much heat and time. The most interesting was finding one while stuck on the hard shoulder .
Andy
 
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Couldn't agree more with Clem.
Also, any fuse will fail from corrosion, so don't hesitate to add a smear of grease to any contact points, then check from time to time.
The electrical connections on a motorbike aren't maintenance-free...
😉
 
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Exmoor beast said:
Cheapo fuse- but also check the tension in the holder
Click to expand...
I secon the tension of the holder... My brother once got a 1000 SFC in exchange for his 120° Jota because the 1000 SFC died always out of blue while riding. It was a fuse that lost contact which he only found because at one point, it droped out of the holder and made the engine stall. He took off the seat, looked at the fusebox, found the lose fuse, recognized it does not sit tightly in the holder and bent the ends of the holder so it was sitting firmly. Engine never stalled on its own from there... Cheep upgrade from a 120° Jota... :LOL:
 
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