How to tell if a car fuse is blown?

A car fuse is a small but essential part of your vehicle, and if it has any damage, it could drastically impact your ability to drive.

In this car maintenance guide, we look at the symptoms and what you should do if your car fuse has blown.

What is a car fuse?

A car fuse is a compact safeguard built into your vehicle’s electrical system that has many purposes.

When too much electrical current flows, the fuse sacrifices itself by breaking the circuit, preventing damage to wiring and components.

Without it, everyday features like headlights, entertainment systems, sat navs, air conditioning, or sensors could be at risk of overheating or short‑circuiting.

Most modern cars use blade‑style fuses, easily identified by their coloured plastic casing.

When one blows, the affected system stops working until replaced, keeping the rest of the vehicle protected and running safely.

How to tell if a car if a car fuse is blown

You will notice that a particular system in your vehicle is no longer working.

Although there are many potential causes, one of them is a blown fuse.

Car owners will need to start by locating the fuse box, which often found under the dashboard or in the engine bay.

The next step is to remove the damaged fuse and hold it up to the light. This is because inside, you’ll see a thin metal strip. If that strip is broken or burnt, the fuse has blown.

Some modern blade fuses also show discoloration or a cloudy appearance when faulty.

Another giveaway of an issue with the fuse is a sudden failure of an electrical feature, like headlights, radio, or power windows.

After replacing the broken fuse, if it blows again, it signals a deeper electrical issue that needs professional attention.

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What does a blown fuse look like?

A blown car fuse usually shows clear visual signs that are easily recognisable.

Here are the signs to looks for:

• The metal strip inside the fuse is broken or melted
• Blackened, burn marks, or discoloration inside the plastic casing
• Some fuses look cloudy or smoky when they’ve failed

Essentially, instead of a continuous metal link, you’ll notice a gap or burn where the strip has overheated and snapped.

What should you do if you have a blown car fuse?

If you suspect a blown car fuse, the safest step is to avoid attempting complex repairs yourself and leave it to a mechanic.

In many cases, a blown fuse often indicates an underlying electrical issue and simply replacing it may not solve the problem.

While some drivers can check fuses at home, if your vehicle has broken down or you’re unsure, it’s best to leave the inspection to trained professionals.

An RAC Approved Garage can diagnose the fault properly, replace the fuse, and ensure no further damage occurs.

This protects your car’s electrical system and keeps you safe on the road.

Step-by-step guide on how to replace car fuse

This is what a qualified mechanic will do to replace your blown car fuse:

• Safety first: Park safely, turn the ignition off, and remove the key.
• Locate fuse boxes: Common locations are under the dashboard, in the glovebox, or in the engine bay.
• Identify the circuit: Use the fuse box diagram (on the cover or in the owner’s manual) to find the fuse for the failed component.
• Remove the fuse: Use the plastic fuse puller or pliers.
• Inspect the fuse: Check the tiny metal strip to see if it’s broken, burnt, or discoloured.
• Match the rating: Replace only with the same amperage (colour and number should match what is in the car owner’s manual).
• Install the new fuse: Push it firmly into the slot until seated and clicks into place.
• Test the component: Turn the ignition on and confirm the feature works.
• If it blows again: This indicates a deeper electrical fault, and you should speak to a mechanic.