Is there a fuse that fixes itself?
Fuses do not fix themselves. They burn out, when you blow a
fuse, and cannot be fixed. However, circuit breakers are designed
so that they turn off the current when it exceeds a safe level, but
afterwards they can be reset. This is much more convenient than
using fuses. But even circuit breakers usually do not reset
themselves, someone has to reset them.
You probably shouldn't use one.
The single most important job of a fuse is to prevent the flow
of electrical current when some condition occurs. That condition
may be the maximum safe amount of current flowing in a circuit. It
could be the maximum safe temperature around the fuse being
reached. Inside an ECM or BCM (vehicle computer) fuses may be
set(conducting) at the factory allowing the module to be programmed
and cleared(not conducting) when the module is ready to be
delivered to a customer. These firmware fuses are sometimes
resetable with specialized equipment. Temperature controlled fuses,
often called PTC(positive temperature coefficient) or NTC(positive
temperature coefficient) are almost always resettable automatically
when the temperature returns to normal.
The most common fuse one thinks of is the glass tube or plastic
square containing a short wire and labeled with a number
representing the amps(current) it will allow to flow before that
wire burns up stopping current flow. That type of fuse is a one
time use protection device that sacrifices itself to protect more
complex and expensive equipment it is connected too. The circuits
these fuses are designed for will only blow a fuse if something
elsewhere in the circuit has gone wrong. The fuse is only the
indicator that something has gone wrong, it is almost never the
root cause of a problem. Because the fuse takes a certain amount of
time to blow after the excess current condition occurs, it can
still allow damaging levels of current to reach the protected
equipment for brief periods. Therefore it is very unwise to just
keep replacing fuses in a circuit that blows them. It is even worse
to replace the fuse with a resettable device such as a circuit
breaker or automatically resettable circuit breaker.
These devices do exist. They operate on the principle of a
temperature controlled fuse. Higher levels of current through a
fixed resistance cause increased heat production. A bimetalic strip
expands and breaks contact instead of burning an internal wire.
When the bimetalic strip cools, the contacts can be reconnected.
The major problem that can occur with these devices is the spark
produced at the contacts when they make or break. The contacts can
weld themselves together with the heat from this spark, unnoticed
by anyone. This results in an unprotected circuit and possible fire