Funny fuse

Odd that this subject surfaced now. I just got into my driveway when bike died. You guessed it. Blown fuse. I'll be taking another look at soundness of relevant wire, connectors and components.
Second ride outside my test loop. Finally running beautifully. Noticed I had lost a triple clamp pinch bolt. Others loose.
Probably the only fasteners I didn't check. Seller must have taken lunch (or other type of break) when assembling front end.
Mudguard stays were also about to go AWOL.
 
3CBRG said:
Noticed I had lost a triple clamp pinch bolt. Others loose.
Probably the only fasteners I didn't check. Seller must have taken lunch (or other type of break) when assembling front end.
Mudguard stays were also about to go AWOL.
Click to expand...
Bloody hell! I'd be going over every single nut and bolt on the bike - we're talking potentially very serious outcomes here. Hope the DPO didn't delve inside where you can't see their handywork!
 
I agree with Clem and others that the old bullet type fuses are prone to electrical connection failures. There's a reason why they're re no longer used by the automotive industry.

Fuses are there to protect the electrical system against overload, not to cause whole different raft of problems because of their own inadequacies. Even if they don't blow, they can still fail due to the issues described above.

They've caused a few electrical failures for me over the years too. I replace them with blade fuses whenever I do any re-wiring work on my bikes.
 
Also beware those plastic in-line fuse holders. When I wired the high and low beam circuits through relays and in-line fuses, the cheap plastic fuse body melted and I spent the day thinking I had low beam on.
Needless to say replaced with decent, proper automative fuse holders.
 
Dielectric (insulating) grease is a good product to use for all your connections. Just a thin smear. Don’t be fooled by its insulating properties, the current flows where the metal parts touch, anti corrosion is far more important.
Also, since we are only using 12v, any grease will do (except on HT leads!) but normal grease will melt away if it gets hot.
 
not wanting to get involved, but the very nature of a fuse is to get hot... to do its job, it must fuse!!. If its a copper or silver fuse filament , the metal strip (at its thinnest point) needs to get to around 1000C before it will fuse. Lead and tin fuses are much less, around 300C, I think. There is not much 'plastic' that can handle that kind of heat without distorting under tension etc. hence the reason porcelain is used in quality fuses and holders. All fuses will be 'hot' if they are operated anywhere near their Amp rating. The filament must be hot & ready to rupture if the current exceeds the rating. Quick blow fuses are designed to operate at elevated temps for that reason.

The above should not be confused with poor connection / high resistance joins causing heat. Just sayin!
 
Yeah, but current flow under normal operating conditions is usually nowhere near the current rating of the fuse. So they shouldn't get hot when the system is working as it should. They're just the weakest link in the chain and their job is to melt before the wiring harness does when something goes wrong.
 
  • Like
Reactions: IAG
Yeah, but think hot joints. They happen when a bad connection is made. Plastic terminal blocks fry due to hot joints inside them, there’s no reason for plastic fuse bodies not to do the same.
 
All true, and I think we’re all on the same page, but maybe looking at different lines on the page...
The fuse in question will stay within temperature limits at the terminal ends, if the connections are good. The actual fusing parts have a higher resistance and will run much hotter, but the plastic parts are protected from that extra heat by being slightly separated at that point.
Also, for interest, fuses actually wear out with use, because of heat damage, especially when used at close to their rated current. An old fuse can blow at a far lower current if it’s had a hard life.

I had a WW2 veteran uncle who was a bit like that...
 
Hmm bullet fuses so that is what you lot call them in the trade they were simply referred to as Ceramic fuses and as the name suggests the original design was the filament over a ceramic body.. yep now they use plastic which is fine until it gets too hot however technically the fused material should fail first. If its getting hot and melting as yours is then would suggest to me that there is a poor contact there which causes a high resistance which then produces heat in that area... so I would suggest that as per others you ensure that the contacts on the fuse tangs are clean and free from oxidisation which is the usual culprit then yes dielectric grease is good but first you need to ensure that the contact surfaces are well clean otherwise its like putting a bandaid on a major cut ... . The usual issue on these old fuse box’s is that the tangs over time loose their tension so then they become corroded and you end up with poor contact.
Simplest thing to do is to clean the tangs rebend to make good contact, apply a small amount of dielectric grease then once you fit it ... test across the fuse at the outputs of both tangs for any voltage drop ... ideally you should only be seeing .01 or so of a volt if you are seeing much more than that then this is the reason why its melting ... I would also do the same test back to the battery to see if there is excess load somewhere else in the circuit.


Oh Quentin best you go back to page 1 of this thread and you will soon gather what Marty is discussing ... think all things considering the 120 Jota was the right decision ... esp if you consider the amount of hard yards it does for Marty 😂 haven’t seen any SFC1000’s round him up ... of late well maybe except for Chris but that’s usually cause Marty has slowed down to have a rest 😢
 
You must log in or register to reply here.
Back
Top