On Sun, 21 Nov 2010 09:15:27 -0600, bud--
wrote:

wrote:
On Sat, 20 Nov 2010 08:50:26 -0800, Smitty Two
wrote:

In article ,
wrote:


I have seen many fuses "just fail" over the last 50 years, both
automotive and "mains". And like incandescent (filament) lamps, I've
seen them "mend" themselves temporarily - sometimes several times,
before final total failure.
An intermittent "failed" fuse can really be a bugger when
troubleshooting an intermittent electrical problem.
Failed fuses don't mend themselves. However, a common automotive failure
is intermittent connections behind the fusebox. Pulling and replacing a
fuse restores the connection, for a minute, day, or week.


I beg to differ. The fuses can arc weld themselves back together and
work for a while, then re-fracture. Depending on temperature changes
etc, this MAY happen more than once, but even once is a rare
occurrence. Rare, but it happens.

On most current automotive fuse boxes there are no "connections"
behind the fusebox that would be influenced by removing the fuse. -
and replacing the fuse invariably solves the problem - often for the
remaining life of the vehicle.

Same thing happens in fused distribution panels - both with plug
fuses (the round glass screw-in common fuse) and with cartridge fuses,
on occaision. Bump the fuse, or have the temperature go up a few
degrees, and the fuse makes contact again, allowing light loads to
operate. Sometimes they will "weld" themselves and not cause a problem
again for several days.
Looking at the fuse there is no sign that there is anything wrong -
but sometimes if you tap the fuse in the dark you will see a faint
blue arc inside the fuse body, and a light connected to the circuit
will either flicker off, or faintly flicker on..

Maybe it happens in Canada. Very doubtful in the US.


Dang fuses were "made in USA" And they don't know if they are in
Detroit or Windsor. The fuse may fracture when cooling off with no
load - "the light worked last time I tried it" - no arcing, no
melting, no sign of failure.
Fuse elements on power systems burn a gap when they open. The fuse
elements are almost always quite rigid and can't vibrate back together.
I really don't think UL would like that behavior.

They burn a gap when they "blow" Rigidity of the fuse element causes
fatigue from repeated cycling.- right at the soldered joint to the
shell.

As far as the UL is concerned, they don't really care because it is
NOT a safety issue. Can't cause a fire or any other damage

In many years in the industry I have not seen a fuse "just fail". Maybe
you could buy bootleg fuses from the US.