Blade Fuses

Paul Sutton

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Cardiff UK
Those stock fuse boxes do not age well so many have opted to replace with blade fuses. Unfortunately blade fuses do not always provide a snappy response to a short circuit as was the case with those original glass fuses. Generic blade fuses may be responsible for melted wires due to excessive response time. The following video demonstrates this issue:

From the specification tables shown in this video you can see that a blade fuse melts in about 0.3 seconds when subjected to twice it's current rating. However, if subjected to values just over their current rating they can take many minutes to blow. Blade fuses are very slow blow until you get to about 2x current rating.

For a more detailed analysis see the following:

The issue with Generic/Cheap blade fuses is their resistance is too low - typically about 1 milliohm i.e. 1/1000th of an Ohm. Blade fuses made to the correct specification have resistances in the region of 2 - 7 milliohm depending on the fuse's current rating. It is these very small differences in resistance that lead to fuse heating and melting when the current rating is exceeded. Consequently a cheap generic fuse may take many minutes to blow while your wiring heats up and the insulation slowly melts.

I have dumped all my blade fuse today and ordered in OEM quality fuses (Littelfuse). Essentially my Ebay bargains were just pressed metal that look like the real thing, what about yours...:umm:
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I have dumped all my blade fuse today and ordered in OEM quality fuses (Littelfuse). Essentially my Ebay bargains were just pressed metal that look like the real thing, what about yours...:umm:

I'm gonna do the same. Leave it to the Chinese to screw up even a fuse. Kinda odd given that materiel composition and size is actually published data in the form of industry standards.
There's really no excuse except for complete disregard for quality in the name of maximizing profits.
Well drats ... the fuse on my Cx500 trike would go out about every third key on...... I got the last 4 my dealer had.... $1.25 a piece... needless to say the local auto store didn't carry this flat metal style I made a blade 30 amp replacement..... since I installed it.... no issues.... now... ? I wonder.... I hate electrical... Aaaaaaaaaaargh 😎


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Whoaw-wow how do we measure such things?

Without a u tube vid.

The bikes manual will provide the fuse size ..... some bikes have one fuse.. my 82' Special has .. four.... the fuse box for these Specials were known to turn green and fail... Mile's offers a replacement... your local auto store has one also... I replaced mine with the auto store piece. 😎
In the UK the Bussmann fuses are very rare. The Littelfuse brand exists but is generally a bulk buy on Ebay - Probably worth buying then dividing into smaller lots to resell. MTA seems the easiest option on Ebay UK and they are a real fuse manufacturer with specifications on their website.
Very interesting topic. There is one 20 amp fuse on my '74 TX650A. I converted it to a blade fuse a few years ago because the wiring was a bit suspect by the PO at the fuse holder. I just went out to check it and I cannot find any brand name on the fuse. I will be buying a brand name fuse before I ride the bike again.
Good thread Paul. Woke, (NO), something that has been in the back of my mind bugging me when ever i have looked at and bought/used these cheep fuses.

This should be in the Tech menu under a heads-up/warnings heading
When I was going to night school as part of my apprenticeship we were taught that rewireable fuses the type that were used in domestic situations had a fusing factor of 2. Meaning that it would not clear under 2 x its rated current. It was termed coarse excess current protection from memory.

Not knowing any better I always assumed that the glass tube wire fuse and blade type fuses have a similar fusing factor and regard them as providing short circuit protection only with no overload protection.

When wiring a bike I give no consideration to overload protection as the loads are known and use fuses for short circuit protection. I still intend to use blade type fuses as they have features I like. The ability to test them in situ springs to mind.

The take away for me is to use name brand fuses that have quality control. Provided you can find them that is, the hunt is on.
Wingedwheel - Great choice to buy the Littelfuse Smart Glow fuses...:hump: As we all know, fuses only blow at night when there is no lighting nearby. For this same reason I bought the fuse holder with the built in LEDs to show which fuse blew.
At a bare minimum, a product should do what it is supposed to do. A cheap product may not last as long, not be easy to use, break easily, but should still perform its basic function.
A 5 amp fuse that woun't blow at 20 amp is flat out fraud. Is there no law for this?
I've been discussing this in my classes for at least a decade now. The 'Storehouse'- and other off-brand fuses aren't really fuses. They just look like them and fit in their place. The metallurgy is completely wrong. I do a demonstration with an inductive ammeter probe on a PICO scope, and a vehicle lead-acid battery. I use an 8awg battery cable with alligator clamps, connected to each leg of the 'fuse'. I've had 10A devices hold up to 90A, while glowing and melting the plastic body.
Went through my collection of ATO fuses and found the majority of them were Little Fuse or Buss. 👍 Only had one that wasn’t branded and tossed it. Found several that had Hanson or Pacific molded into the body. Appears they are a legit, quality manufacturer so I’ll keep those. The mini fuses are a mix of Little Fuse and no name. The no name came from an electrical component vendor back when I was still working. That’s all we put in our equipment. Scratching my head whether I should toss these.