How do I check whether a fuse has blown?
A fuse protects an electrical circuit by interrupting the current if the load becomes too high or a short circuit occurs.
If an electrical function in the car stops working, a blown fuse may be a possible cause.
1. Find the correct fuse
Start by checking the car’s owner’s manual or fuse diagram.
This usually shows which fuse belongs to each function.
Fuse boxes may be located in several places in the car, such as the engine compartment, dashboard or boot.
2. Inspect the fuse visually
Switch off the relevant equipment and follow the car’s instructions before removing the fuse.
Many common blade fuses have a transparent casing that lets you see the metal strip inside.
If the metal strip is broken, the fuse has normally blown.
However, it is not always possible to determine the fuse’s condition just by looking at it.
3. Check the fuse with a multimeter
A fuse can also be checked with a multimeter.
Switch off the power supply to the circuit.
Remove the fuse.
Set the multimeter to continuity or resistance measurement.
Place one probe against each terminal of the fuse.
Read the result.
An intact fuse normally has very low resistance and often produces a beep if the multimeter has a continuity function.
A blown fuse normally shows an open circuit, such as OL on the multimeter’s display.
Can I replace it with a higher-rated fuse?
No. A blown fuse should normally be replaced with a fuse of the same type and current rating.
For example, a 10 A fuse must not be replaced with a 15 A fuse to prevent it from blowing again.
A higher-rated fuse may leave cables and components without the correct protection, potentially causing overheating or fire.
Why does the fuse blow again?
If a new fuse blows immediately or after a short time, there may be an underlying problem.
Common causes include:
A short circuit in a cable or component.
Excessive load on the circuit.
Damaged cable insulation.
Incorrectly connected aftermarket equipment.
A faulty electrical component.
Do not repeatedly replace the fuse without investigating the cause.
If the fuse keeps blowing, the circuit should be checked before the equipment is used again.