The job of fuses is to protect the car's electrical circuits. Fuses used in automobiles consist of a glass-enclosed strip of alloy metal having a low melting point. If for some reason a circuit becomes overloaded, the fuse will blow; but when this happens the wiring and the components it serves will be protected from damage.

Modern cars have several different electrical circuits for different systems (e.g. for the headlights, parkinglights, wipers, audio, cigarette-lighter, etc). Along with the main fuse-link different fuses are placed for each circuit, to protect the electrical equipment should a short or serious overload occur. Each circuit has a specific fuse value ranging between 5-25 amps.

Connected Line Fuse

Disconnected Line Fuse

Should a fuse blow, or in the event of dirty fuse or holder:-
Clean the fuse holder if fuse is serviceable.
Switch off everything including ignition switch.
Replace the fuse with one of the same value (for convenience there are specific color codes for specific ampere values or the rating of each fuse is normally specified on it).
If the replacement fuse also fails as soon as it is fitted, check the components and wiring for a short-circuit.
If the fuse does not blow, switch on each accessory branch until the fuse blows, thus indicating the faulty branch.
Inspect closely for defective accessory or wiring.

A circuit may fail although the fuse has not blown, if the fuse becomes dirty or corroded, or if it is shaken loose by the vibration of the car. Cleaning or tightening the holder usually cures these faults.

There is no safe substitute for a fuse. The use f silver paper wrapped around a match or blown fuse, for instance, can result in extensive damage if there is a fault in a circuit or component.