There’s a lot of confusion when it comes to the fuses in your car. For starters, did you even know that you have one or two dedicated fuse boxes hidden somewhere in your car? Fuses play a massively important role in your vehicle and they can save you a ton of money.
In this guide, we’ll explain all the facts about car fuses. We’ll tell you what they are, what they do, whether or not they can wear out, and how to find and check the fuses in your car.
What Do Car Fuses Do?
Just about everything in your car with a wire has to go through a fuse. If too much current tries to go to your device, the fuse will fail and take the bullet for your device. Why? It’s a lot easier to replace a fuse than your ECU, horn, cooling fans, and ABS system.
These sacrificial fuses can be found around your home too, and they serve the same purpose. Within your car, they come in a few different sizes.
Different Car Fuse Sizes
Cars can have any combination of six different fuse sizes. They’re not just physically larger or smaller, but the maximum current that they’re rated for is different, too.
You can find fuses anywhere from 0.5 amps to 120 amps. Within this range, you’ll find different colors that indicate the size of the fuse so you don’t need to break out the ruler. Dark blue has the lowest current rating and purple has the highest.
In a lot of cases, you’ll probably find a mini, regular, or maxi fuse size in your vehicle.
Can Car Fuses Wear Out?
As we just mentioned, fuses are meant to burst and break when there’s too large of a current, but can car fuses wear out? The answer is a little tricky, but technically they don’t “wear out”.
Transmission or engine definitely wears out over time. The pieces rub together, degrade over time, and eventually break. If you take good care of your car, “eventually” should be decades, but still.
In the case of fuses, there’s nothing mechanically happening that will wear them down. What happens instead is the electrical components get shaken loose and the fuse can break.
This happens when a door slams, you hit a speedbump or any vibration over time. These vibrations can knock the contacts loose in the fuse. The contacts are the electrical components that complete the puzzle and allow the current to flow through the fuse. Without contacts, the fuse might as well be blown.
So, this is why the answer is a little tricky. It’s not a matter of parts wearing out or deteriorating over time – it’s just a matter of bad luck knocking contacts out of position.
If you have a perfect fuse and you feed it justifiable current over time, the wires won’t degrade and the contact won’t wear out. This is true for small or large fuses alike.
Remember, Fuses Are Meant to Break
Even though a fuse doesn’t wear out, it will break. The confusing part is that when a fuse breaks, it’s actually doing its job.
Remember, these fuses in your car are sacrificial pieces. If they detect a current that can harm your vehicle’s components, the fuse will “blow”, or break. After that, the fuse won’t work anymore until you replace it.
In some rare cases, a fuse can break below the current threshold. If it sustains a current that’s slightly below its rated max for a really long time, the fuse might prematurely break. If you’re looking to replace a fuse, you need to know where to find it.
Where Is the Fuse Box?
The fuses will be located in a fuse box that typically contains a lot of different fuses. Car manufacturers like to hide them in different places when they’re designing cars, so you’ll have to do some digging.
Some common places are:
- Under the hood. A lot of cars have at least one fuse box under the hood. This is where the bigger fuses are stored. It should be a little black plastic container with some type of marking on the lid that indicates it’s filled with fuses.
- Under the dash. You might see a little pop-out section under your dashboard. Once removed, you’ll gain access to the fuses and there should be a fuse map on the inside of the piece you remove.
- To the left of your steering wheel. Same story as the removable dash piece.
- Behind the glove box. Open your glove box and look at the back or top surface. If either surface has a little flap and a “FUSE” label, pull it. It’s probably a door that leads to your fuse box.
- In the trunk. BMW designers had to look pretty hard to find a place to put their fuse box. Some of their models feature a fuse box behind the carpeting trim in the trunk.
Still not sure where it is? Take a look in your owner’s manual – they should clearly spell out exactly where the fuse box is and how to access it.
Once you find the fuses, you should check to see if any are blown.
How to Check Your Fuses
There are two major ways to check if your fuses are any good. Since you don’t have to look for normal wear and tear, you’ll just be checking to see if the fuse is working or not.
Check for Signs
Fuse manufacturers realize that you probably don’t have specialized tools to take apart a fuse (nor do you want to). For that reason, they add a little window in the fuses so you can take a quick look.
In the glass window, take a look at the filament. This is the wire that runs across the fuse that does all the work. If it’s melted or broken, your fuse was blown. In other words, if the filament isn’t making a continuous line across the fuse, it’s blown.
You can also check for burn marks on the viewing glass. This is an indication that the fuse blew without completely separating the filament.
Use a Fuse Testing Tool
You can also grab a specialized fuse testing tool:
Katzco Voltage Continuity and Current Tester – 6-12 V DC – 24 V AC Circuit – Heavy Duty
You simply clamp the ground to a piece of metal in the car and test all the fuses.
Turn your key in the ignition to “run” (you don’t have to completely start the car). Use the metal probe and touch the different fuses you want to test. If the light in the handle turns on, then the fuse is okay. If it’s dark, then either the fuse is blown or you’re not touching the fuse correctly.
Now you’re the fuse expert. At this point, you should know where the fuses are, what they do, and how to test them. Fuses are designed to break, but they don’t wear out in a traditional sense. Armed with this information, you can avoid a trip to the mechanic. Check out our blog for more car tips and tricks, and make sure you have the right tools and accessories for the best driving experience.