How to Check if a Fuse has Blown in Your Car

Jack Dreyer | Friday 23rd September 2022 11:58am

A gloved hand uses a fuse puller to remove a green fuse from a fuse box in a car.

If you’ve owned your car for long enough, the chances are that you’ll encounter a blown fuse at some point… It’s quite a common problem, after all.

Car fuses – also called ‘automotive fuses’ – are crucial components that, like regular fuses, are specifically designed to protect the electrical wiring of a car. Their primary function is to offer protection against overcurrents and things like short-circuiting. They simply disconnect the circuit if a potentially-dangerous level of current threatens to pass through.

But what happens when one of these fuses blows? Read on to find out.

Automotive fuses

Close up of different blade fuses in a car's fuse board showing different amp ratings.

Car fuses come in all shapes and sizes, with each variation being best suited to a specific application or electrical part in a car.

Most commonly, though, is the blade-type fuse. You may well have seen them: a coloured body made of plastic with two metal prongs to stick into a socket. Depending on the application, these fuses can be mounted into fuse holders, clips, or even blocks.

In a car, a blown fuse will manifest itself as a minor electrical problem such as the failure of interior lights, radio, indicator, or internal features such as climate control. Sometimes, though, it can be as serious as stopping the car from starting altogether.

Why do car fuses blow?

When fuses ‘blow’, the ribbon that allows the current to pass through melts and kills the circuit if too much current passes through. The excessive current comes from an electrical component drawing more than it can handle — this is usually due to a device malfunctioning.

Some of the most common reasons for an automotive fuse blowing include:

  • Defective switches
  • Faulty wires
  • Mechanical issues with motor
  • Rogue faults with electrically-motivated parts

How to check a blown car fuse

If one of your interior lights is no longer working, or your indicator appears to be broken, the chances are a fuse has blown. But now what?

Your first port of call should be to reach out to the professionals. Dealing with the electronics in a vehicle requires not only a steady hand but also expert knowledge. If you’re in doubt, call your local Kwik Fit for further advice — just to be on the safe side.

Out of curiosity, though, if you were to check for a blown fuse in your vehicle yourself, the following steps would need to be carried out.

1. Locate the fuse box

Depending on the make of the car, there may be as many as four fuse boxes located in various parts of the vehicle, and it is important you find the one with the blown fuse. For help, refer to your user manual to determine which fuse box controls which circuit and then go from there. Typically speaking, the following locations are the most common for fuse boxes to be placed:

  • Under the bonnet
  • Beneath the dashboard
  • Underneath the back seats
  • In the boot

Two hands carefully lift a fuse box up from underneath the bonnet of the car. It is still attached to the car and wires are visible.

2. Locate the individual the fuse

When you have located the culprit fuse box, you will need to identify the suspect fuse. Luckily, to make things easier, most fuse boxes will have an intricate diagram explaining the function and location of each fuse. If your fuse box does not come fitted with this luxury, you’ll have to use a test light. (This is now getting highly technical and would definitely be better left to the experts!)

If you are using the test light method, though, be sure to use a computer-safe one with an LED light. You will have to have the car running for this - but not fully. Just have the ignition on, but the engine off. (This is known as the ‘KOEO’ or ‘second key’ position).

Once the ignition is on, attach the clip for the test light to any exposed metal. Then, use the probe to touch each end of each fuse.

  • If the fuse is working properly, the test light will illuminate on both sides.
  • If the fuse has blown, only one side of the test light will illuminate.

3. Remove & inspect the fuse

After turning the car off completely, find your fuse and remove it by grabbing it with a fuse puller (these are usually stored inside the fuse box). If there isn’t one around, a trusty pair of needle-nose pliers will be sufficient too.

Once removed, you can begin to inspect the fuse. Still gripping it with the puller, hold the fuse up to the light (or a light source) and look through the translucent bodywork. You should see a thin metal wire in there. If the wire is no longer a continuous thread and appears broken or in two pieces, the fuse has indeed ‘blown’. If this is the case, it will need to be replaced.

From here you can go on to replace the fuse; however, as we’ve said, it really is best left to the professionals.

Two red plastic fuses have been placed against a white background. On the left, the fuse is broken, while the right one is new and in good condition.

What to do if your car blows a fuse

If your car has blown a fuse, the easiest thing to do is call your local Kwik Fit centre and leave it to us to handle. Dealing with electrical faults can be dangerous and risky, one false move and you may end up doing more harm than good to your vehicle’s electrical system. So, get in touch with us today!

Any facts, figures and prices shown in our blog articles are correct at time of publication.

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