Practically Classics Forum

Can someone provide me with a link to conversion table from glass fuses rated as their 'blow' rating and blade fuses rated as 'continuous' rating?

Specifically I have 35 amp glass fuses, what would the blade fuse equivalent be?

35 amp? as i understand its only the shape that changed..

There are 2 different types, standard and slow blow.
If you have a google you will see the difference but slow blow is something daft like 20 minutes to blow at 200% load.

I don't think Ive seen 35amp blade fuses - only 30 or 40amp. I would try 30amp myself.

35a blade fuses exist. I wouldn't suggest buying fuses on ebay but there are lots available

Moved this to "technical Queries" section......

All types of car fuses have "blow" and continuous ratings. Is there any particular reason for the change?

TerryG wrote:35a blade fuses exist...

Indeed they do, the sunshine roof motor on my current "modern" Japanese transportation device (seen at the left of these words) uses one as do various other of its period sources of entertaining whirring and clonking sounds.

The original fuse box on the Marina was ok and lasted 10 years or so. This fuse box is available new complete with spare fuses.

The glass tube fuses are also ok. I only use the ones with brass caps not plated steel ones.

The old fuse box if left in vingar for a few hours will clean the contacts.

A faint smear of petroleum jelly will stop corrosion.

To calculate amps divide watts by volts to give amps.

Surge.
when an electrical load is applied the amps initially surge. Light bulbs when cold have a lower resistance. So the amps are higher momentarily. Motors are worse surge wise. Such as blower and wiper motors. So when calculating fuse ratings the amps have to be enough to survive the surge. Also note that the surge in motors lasts longer.

Bob

There are two types of fuse: "Slow Blow" and "Fast Blow". Slow blow are actually called "Anti-surge" and are far more suitable for automotive use (though it would be wise to fit fast blow on things like the radio). The continuous rating is normally for Anti-surge and they "automatically" compensate the "start-up load".

There is a common argument as to the purpose of the fuse - the "heavy current" people reckon it protects the device ahead of it, the electronics types tend to think it protects the cable behind it. There are arguments to both opinions but, as an Instrumentation/Control engineer, I reckon most "delicate" devices are shot once the fuse has blown, so the fuse can only protect the wiring! There again, being a "low current" type, I wouldn't normally get much of a shock if I touched a live wire (low voltage and current), where someone working with 33kV would feel slightly more than a tickle if he/she grabbed hold of a live wire!

As with all electrical contacts, a little protection will help them last longer - a bit of vaseline, copper grease or even WD40 is a good idea!

As it happens, I'm rewiring the Land Rover at the moment and it will have (several) blade fuses when I get to that stage. They are more compact and seem to be more readily available than "old fashioned" glass ones (ie the local filling station keeps them!)

Good point about availability of glass fuses.

However when a fuse blows something is wrong.
Neither of my cars blow fuses unless silly me shorted something out. I have spares. I also don't make a habit of shorting stuff out. My 1974 car has its original fuses.

Glass fuses can be repaired by unsoldering and passing a new piece of fuse wire through the fuse.

Question? Continuous rated fuses and slow blow and fast blow. Is the alloy that the fuse wire is made from all the same.

IMHO. Up grades like glass to blade aren't really any better. Its not an upgrade but just different.

Bob.