Fuses are used to break the circuit when the current reaches a certain value, in order to protect elements and wires that can be damaged by too much current. A sudden increase in current is usually caused by a fault in the circuit, most often a short circuit.
The designations of the circuits protected by fuses are indicated on the cover of the fuse box.
Turn off the relevant circuit before removing a fuse (or ignition), then remove the fuse from the contacts. A wire should be visible inside the fuse; if the fuse is blown, the wire will be broken or melted.
Always use fuses of the required capacity. Never use a fuse of a different rating or replace it with something else.
Do not replace the fuse more than once without correcting the source of the problem. The current protected by the fuse is indicated on the top of the fuse: note that the fuses have different colors for easy identification.
If a fuse blows immediately after replacement, do not replace it again until you have installed and corrected the cause of the problem. In most cases, the fault is caused by a short circuit caused by poor insulation. If the fuse is protecting multiple circuits, try to find the circuit that is causing the fuse to blow, including each circuit in turn (if it is possible). Always have a set of spare fuses of different ratings in your car. They must be fixed at the base of the fuse box.