Even if your knowledge of cars is limited, the chances are that you will have heard of a little device known as a fuse. Fuses are in a lot of electronic devices, and so it is no surprise that you will also find a number of them in cars.
Fuses are essential for electronic devices to operate safely as they protect the electrical circuit from overheating and melting. As well as this, most electrical circuits simply will not work if there is an issue with the fuse, so if your car fuse blows, there is a good chance that your vehicle simply will not start.
In fact, a blown car fuse is one of the most common reasons why the electrical components in a car stop working. But how can you tell if a blown fuse is the cause of your problems?
We’re going to tell you how, and lots more about car fuses in this guide. So if you want to find out more then keep on reading.
Understanding Vehicle Electronics
To be able to understand the importance of fuses in your vehicle, you need to have a basic understanding of vehicle electronics.
Generally, you will find that the electrical components of your vehicle will be separated into categories.
These categories tend to consist of:
- Driver assistance
- Chassis electronics
- Transmission electronics
- Engine electronics
- Entertainment system
- Passenger comfort
- Passive safety
- Electronic cockpit system
If you notice an issue in any of these categories of electronics, then there is a good chance that the fuse responsible for that part of the vehicle is playing up or has blown out.
Other than the transmission control and engine control electronics, you will probably be able to fix the issue yourself if the problem lies in the fuse. So it is worth checking it out before taking your vehicle to the garage.
In fact, you are much more likely to experience issues with the fuses responsible for your entertainment system or passenger comfort system than any engine fuses. This is because the fuses located in power sockets and cigarette lighters are much more prone to melting or blowing out than other fuses.
So you will be more likely to experience issues in this category than others, but now let’s take a look at why fuses blow.
Why Do Fuses Blow?
We’ve mentioned that fuses sometimes blow and that some fuses are more prone to this than others, but we haven’t discussed what causes this to happen, so let’s have a look.
A blown fuse is caused by a short circuit within an electrical circuit. In most cases, this short-circuiting is caused by two wires connecting when they are not supposed to, or one of the power wires in the circuit coming into contact with the metal body of the vehicle.
As well as these possible causes, short-circuiting can also be caused by a car part drawing more electricity than it is designed for, so issues with motors in your vehicle can also cause fuses to blow.
But these aren’t the only things that can cause a fuse to blow. Sometimes it can be something as simple as a metal coin coming into contact with one of the vehicle’s power sockets to cause it to blow. It can also be caused by an incompatible headlight being fitted, so there are lots of possible causes of fuses blowing.
A lot of people assume that the first thing that you should do after a fuse blows is replace it, but this isn’t the case. If you replace a blown fuse but don’t fix the route problem of it then this can cause the replacement fuse to blow as well.
So you should identify the cause of the blown fuse before you do anything else.
Fuse Boxes in Vehicles
Depending on the type of vehicle that you own or drive, the number of fuse boxes that you will find inside of it might differ. Generally speaking, most vans and cars have two fuse boxes, but some makes and models can have up to four different fuse boxes within their design.
The location of these fuse boxes will also differ depending on the model of car that you own, so to find out where they are it is best to check your vehicle’s manual.
But if you are unable to find your car’s user manual, then there are some common places where you will find fuse boxes in vehicles, they are:
- In the trunk
- Underneath the dashboard
- Under the hood
- Beneath the backseat
All vehicles will have at least one main fuse installed at the positive battery terminal underneath the hood of your vehicle. So this is usually a good place to start if you suspect you have a blown fuse but don’t know where it could be.
But other than this fuse box, it is best to check your vehicle’s manual to ensure that you are looking in the correct places for your fuse box.
Symptoms of a Blown Fuse
After you have identified where the blown fuse might be, you should trace it back to the fuse box, and then open it.
Most fuse boxes come with a diagram on them that shows you what each fuse is and the position that you will find it in within the box. This will help you easily locate the one that is associated with the part of your vehicle that isn’t working.
However, you should be aware that it is common for more fuses to blow after one goes. This is especially common if it is one of the main fuses that blow first. So once you find the fuse box, it is best to check all of the fuses to see if they are all in operation or if some of the others have blown too.
To check if a fuse has blown, you should begin by giving it a visual inspection. If the fuse has blown it will look as if it has melted, because it has, and you will also commonly find that the metal wire inside of the fuse has broken.
But there are some other ways that you can check to see if the fuse has blown if it doesn’t immediately look broken, so let’s take a look at how you do it.
How to check if a Car Fuse has blown
To be able to check for definite if a car fuse has blown, you will require some tools. You can, technically, remove a fuse by hand, but it is always safer to use the proper equipment to avoid damaging the fuse box.
To confirm that a car fuse has blown, you will need to use a multimeter. You should do this before you even remove the fuse from the box, by checking the voltage on both pins of the fuse. These pins can be found on the upper part of the fuse which is why you can check them before removing the fuses from the box.
With the ignition of your vehicle on, you can then check the voltage of the fuse. On both pins of the fuse, you should get a reading of 12V. If you get a 12V reading on one pin, and no reading on the other pin then this is a sign that the fuse has blown.
The other option you have for checking if the fuse has blown is to check the resistance. You can also measure the fuse’s resistance using the multimeter, all you need to do is change the measurement from voltage to ohms.
Once you have changed the measurement, you can then attach the multimeter to both sides of the fuse, in the same way, that you did to measure voltage. With it attached, you will be able to get a resistance reading.
A fuse that is in good working order will have a resistance reading of close to zero, or perhaps dead on zero. But any resistance higher than this is a good sign that your fuse has blown, and that it will require replacing. So let’s take a look at how you replace a fuse that has blown.
How to Replace a Blown Fuse
So once you have used your multimeter and your eyes to identify that the fuse has blown, it is time to replace it. The first thing that you will need to do is buy a replacement fuse, which you can usually find in a hardware store, or online if you are happy to wait.
But before you buy any fuse, you must buy the right type of fuse, as there are three main types of car fuse. They are:
- Glass fuses with metal ends in a cylindrical shape
- Plastic cylindrical fuses with no cover
- Square plastic fuses with two metal prongs
When you replace the fuse, you must replace it with the correct type of fuse otherwise this could damage the fuse box and your vehicle.
Not only do you have to think about the shape and style of the fuse, you will also have to ensure that you buy a fuse that has the correct amount of voltage. Some fuses have 10 volts, others have 12 volts, so you must buy the correct type of fuse for the fuse box.
When you have a new fuse, you will need to remove the old one. With that fuse taken out, you will then have space to put your new fuse, so all you have to do is put it in the correct space. With the fuse fitted, you should then switch on your vehicle’s ignition to check if the part that was not working is now fixed. In most cases, switching out a broken fuse will fix the problem.
Even if you are not confident that a broken fuse is the cause of the problem, it is always a good idea to check the fuses. A broken fuse is often an easy fix and one that can be a lot cheaper if you do it yourself than if you were to take it to the garage.
But if the issue still persists after you switch the fuse then it is best to take your vehicle to the garage as the fuse blown fuse was probably a result of the issue rather than the cause.
A mechanic will be able to easily identify the problem and fix it, so it is best to get your vehicle checked out if you cannot fix the problem yourself.
In short, if you suddenly experience an issue with the electrical components of your car, then there is a good chance that a blown fuse is the cause.
You can usually tell if a fuse has blown by looking if it has melted, but failing this you can also use a multimeter to tell if a car fuse has blown.