How do I check and replace a blown fuse?

Quick answer

Switch the ignition off, find the right fuse using the chart in your owner’s manual or on the fuse box lid, pull it out with the fuse puller, and look through the plastic: a broken metal strip means it’s blown. Replace it with a fuse of exactly the same rating (the number on top and the colour). If the new fuse blows again, there’s a fault in that circuit that needs finding: never fit a bigger fuse.

Is this a DIY job?

• Difficulty: Easy
• Time: 5 to 15 minutes
• Tools: owner’s manual, fuse puller (often clipped inside the fuse box), torch, test light or multimeter (optional)
• Skills: none

Checking and replacing a blade fuse is one of the simplest car jobs. Finding why a fuse keeps blowing is harder and may need an auto electrician.

Step by step

1. Switch off. Ignition off, key out, and switch off the item that stopped working.
2. Find the fuse boxes. Most cars have at least two: one under the bonnet and one inside the cabin (under the dash, in the side of the dash, or behind a panel in the footwell or glovebox). Some have more, including one in the boot. Your owner’s manual shows where.
3. Find the right fuse. Use the chart in the manual or on the inside of the fuse box lid. Fuses are labelled by position, rating and the circuit they protect (for example “CIG”, “RADIO”, “P/W”).
4. Pull the fuse out. Use the plastic fuse puller, or fine-nose pliers, gripping the plastic body. Pull straight out.
5. Check it. Hold it up to the light. A good fuse has an unbroken metal strip between the two blades. A blown fuse has a gap or a melted, blackened strip. If you can’t tell, test it: with a multimeter on continuity or resistance, a good fuse reads close to zero ohms. Many blade fuses also have small test points on top, so you can test them in place with a test light (ignition on for circuits that are only live with the ignition).
6. Fit an identical replacement. Same type (micro, mini, standard or maxi), same rating (number on top), same colour. Push it fully into the slot.
7. Test the circuit. Switch on and check the item works.
8. If it blows again straight away, stop replacing fuses. There’s a short circuit or an overload in that circuit.
9. Replace your spare. Many fuse boxes have spare fuses clipped inside. Replace any you use.

Checking a relay

Relays are the larger plug-in cubes in the fuse box. They switch high-current items like headlights, horns, fans and fuel pumps. A simple check: with the ignition off, swap the suspect relay with an identical relay (same part number) from a circuit you can test, such as the horn. If the fault moves with the relay, the relay is faulty. If you’re not sure two relays are identical, don’t swap them. (see How do I wire a 12V relay (pins 30, 85, 86, 87)?)

Specs table

Standard blade fuse colours (regular, mini and micro blade fuses)

Not every rating is made in every size, but where a rating exists the colour is the same.

Maxi fuses use a different colour code. For example, a 50 A maxi fuse is red and a 60 A maxi is blue. Always go by the number printed on the fuse, not just the colour.

Fuse types by size

What you’ll need

• mini blade fuse kit / standard blade fuse kit / micro blade fuses (whichever your car uses)
• fuse puller
• 12V test light or digital multimeter
• automotive relay (if a relay has failed; match the part number)

When to call an auto electrician

• A fuse blows again after replacement. There’s a short or overload to find.
• The blown fuse protects the airbags/SRS, ABS, engine management or a module. Don’t keep replacing these: get the fault diagnosed.
• A large bolt-in, cartridge or main fuse has blown. These protect major circuits and often point to a serious fault.
• Fuses, relays or the fuse box show signs of melting or heat damage.
• It’s a hybrid or EV and the fault involves the high-voltage system. Never touch orange cables or high-voltage fuses.

Related questions

Q: Can I use a higher-rated fuse if I don’t have the right one? A: No. The fuse protects the wiring. A higher-rated fuse can let the wiring overheat and start a fire before the fuse blows. Never replace a fuse with wire, foil or any other metal object, even to get home.

Q: Can I use a fuse from another circuit temporarily? A: Only if it’s exactly the same rating and from a circuit you don’t need, such as the cigarette lighter. Replace it with the correct fuse as soon as you can, and never borrow from safety systems.

Q: Why does my fuse look fine but the circuit doesn’t work? A: Fuses can crack internally where you can’t see it, so test it with a multimeter or test light. If the fuse is fine, check the relay, switch, wiring and the item itself.

Q: Where’s my car’s fuse box? A: Most cars have one under the bonnet and one in the cabin, and some have one in the boot. The owner’s manual shows the locations and what each fuse does.

Sources

1. Littelfuse, ATO and MAXI blade fuse datasheet (via Farnell) – blade fuse colour codes by rating; maxi colour code differs. https://www.farnell.com/datasheets/82316.pdf (checked October 2026)
2. ISO 8820-3 – Road vehicles, fuse-links, Part 3: fuse-links with tabs (blade type). Referenced as the standard behind the colour code; not quoted.
3. Volvo Cars Australia, “Replacing a fuse” (V90 owner information) – replace with the same colour and amperage; a higher-rated fuse or a foreign object can damage the electrical system and cause a fire. https://www.volvocars.com/au/support/car/v90/article/97f7da007063b1e3c0a8015164d3df7a/ (checked October 2026)
4. Kia owner’s manual, “Fuse replacement” – same rating only; a fuse that blows again means an electrical problem; never use wire or foil in place of a fuse. https://ownersmanual.kia.com/full_webhelp/KA4/2024/en_US/topics/t00732.html (checked October 2026)