Why is an electrical fuse burnt?

An electrical fuse would look "burnt" if something in the circuit it is protecting has developed a fault which caused a current overload situation to occur.

In other words, something caused the current flowing through the fuse to exceed its normal rated maximum current value so much that the fuse did what it was designed to do!

In this situation, if a new fuse of the same value immediately blows, do not attempt to replace it by a fuse having a higher rated current value. The correct procedure is to find out what went wrong in the circuit that the fuse is protecting and then get the problem fixed so that the equipment works properly again without blowing a new fuse having the same rated current value as the original fuse which looked burnt.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.