How to Safely Identify and Replace an Auto Fuse

Fuses are the unsung heroes of your vehicle, working to prevent current from overloading your electrical system. Most cars or trucks contain around 90 individual fuses and yet, if you’re like me, they’re a part of auto maintenance that you rarely think about. So, what should you do when you have a blown fuse? Follow these easy steps to replace a fuse properly.

How to Identify a Blown Fuse

As mentioned above, vehicle fuses are a safety device designed to keep your electrical system from overloading. If the current in your car or truck exceeds the safety rating of the wires or components, the element within the fuse will melt in order to stop the flow of electrical current. Components that use fuses include your vehicle’s radio, horn, windshield wipers, as well as exterior and interior lighting.

So how do you know if a fuse has been blown? If your car’s battery and alternator are performing properly, but a single electrical application won’t work, it’s most likely due to a blown fuse. For example, let’s say that your radio has stopped working, but all the other electrical components in your car are performing normally. That’s a good indication that you have a blown fuse.

Fixing a Blown Fuse: Getting Started

The first and most obvious thing you want to do before you go poking around in your vehicle’s electrical systems, is to make sure that your engine is turned off and that the key has been completely removed from the ignition. This is very important to insure you don’t suffer any electricity-related accidents.

Next, you’ll want to get your hands on the owner’s manual that came with your car or truck. This will show you where all of the various fuse boxes are located, which can vary significantly from vehicle to vehicle. Can’t find your owner’s manual? Don’t worry, most owner’s manuals can be found online by searching for your specific car or truck.

Now that you’ve got your owner’s manual handy, it’s time to locate the fuse box. Most vehicles have more than one, so use your manual to locate the fuse box related to the application that has stopped working, like the malfunctioning radio we mentioned earlier. Some common locations for fuse boxes include beneath the steering wheel, under the floorboards, in the trunk or under the hood.

Finding the Fuse Box Inside Your Vehicle

The fuses themselves are usually found behind a panel or cover that can be easily removed. Often times, there is a diagram on the fuse box itself or on the back of the the cover detailing what application each fuse corresponds to.

The fuses themselves will appear as a bunch of small colored objects with numbers written on them. If your car has Littelfuse brand fuses, these colors will indicate the amperage of the fuse, which will also be written on top of the fuse itself. Before you go removing any of them, it's a good idea to take a picture of where the fuse you're replacing is located using your phone. That way, you won’t lose track of its location once the fuse has been removed.

Once you’ve located the fuse you need to replace, it’s time to remove it. Many vehicles include a small plastic tool called a fuse puller on the inside of the fuse box cover. If you don’t have a fuse puller, you can also use a small set of pliers in order to remove the fuse.

What are the Different Type of Automotive Fuses?

Now that you’ve removed the fuse, it’s time to figure out just what type of fuse you have. There are quite a number of different fuse types which are detailed below. Keep in mind that vehicles often use a combination of different fuse types, so you may have several of these in your car.

Blade Fuses – These flat fuses feature 2 prongs, or blades, on one side which easily plug into the fuse box. Types of blade fuses include ATO, MINI and Low Profile MINI. The ATO version is much larger than the MINI versions. The Low Profile MINI fuse has the 2 blades running along the outer sides of the body, rather than jutting out below.

Cartridge Fuses – Cartridge fuses are box-shaped and feature a hole in one side that plugs into the fuse holder. Cartridge fuse varieties include the MCASE, JCASE and Low Profile JCASE. JCASE fuses feature a double spring-beam box terminal with a secondary locking feature to hold the fuse in place more firmly. JCASE fuses are used in many new domestic, European and Japanese model cars and can be found in our Emergency Fuse Kits for Chrysler/Dodge/Jeep and Kits for VW/Audi. Low Profile JCASE fuses are available in our Emergency GM Kits and Ford Kits.

Bolt-Down Fuses – These large, flat and rectangular fuses have 2 metal terminals on each side containing a size M6 bolt mounting hole. Unlike blade or cartridge fuses, bolt-down fuses are secured to the fuse holder with a screw, nut or bolt. The two types of bolt-down fuses available are MEGA fuses and the much smaller MIDI fuses. MEGA fuses are OEM (original equipment manufacturer) components for Ford, GM and Chrysler vehicles. MIDI fuses are also OEM on vehicles from Chrysler and BMW.

Glass Fuses – Glass fuses are cylindrical in shape with a clear glass body and 2 metal contact points or caps at each end. Glass fuse varieties include the AGA, AGW, AGC, AGX and SFE. All of these are 1/4 inch in diameter, but vary in length and amperage (which will be engraved on the metal ends). Glass fuses are typically found in cars made prior to 1981.

Thermoplastic Ceramic/Torpedo Fuses (GBC) – These torpedo-shaped fuses have a thermoplastic body with a metal fuse element stretching over the exterior of the body from end to end. All GBC fuses are 6 x 25mm. Their bodies vary in color by amperage. The 5 amp is yellow, the 8 amp is white, the 16 amp is red and the 25 amp is blue. These types of fuses can be found in many European cars.

Replacing Your Vehicle’s Fuse

After you’ve successfully identified the type of fuse you need to replace, be sure to take note of the proper amperage. Your replacement fuse must have an amperage rating identical to the original fuse. Using a fuse with an incorrect amperage can cause serious electrical problems.

With the new fuse in place, it’s time to start the ignition. Everything should be working properly now. If not, it most likely means that your issue wasn’t related to fuses and it’s probably time to bring your car into the shop.

Having trouble locating a replacement fuse? No problem. Simply stop by your nearest Batteries Plus Bulbs location. Our experts will be happy to help you identify any fuse and make sure you get the right replacement. Or, shop our selection of truck and auto fuses online.