How To Car Tech Car Fuses and Fusible Links Explained Blowing the lid off car fuses and fusible links Share Pin Email Print Car fuse colors indicate the amperage they can handle, but they are also printed with an amperage rating. Gary Gladstone / Stockbyte / Getty Car Tech Basics Guides & Tutorials Installing & Upgrading Tips & Tricks Key Concepts by Jeremy Laukkonen Jeremy Laukkonen is a tech writer drawing from experience as a technology ghostwriter and as the creator of a popular blog and a video game startup. Updated October 23, 2018 61 61 people found this article helpful Automotive fuses are the gatekeepers and bodyguards of the automotive electronics world. Whenever a sudden short or surge threatens any of the delicate electronics found in modern cars and trucks, a fuse stands ready to valiantly throw itself into the field of fire. In doing so, the fuse takes a figurative bullet for some more valuable, complex, or indispensable component or device, like a car stereo or amplifier. This often results in some temporary loss of functionality, but fuses are cheap, and usually easy to replace, and any underlying problem will typically be revealed by repeated failures of a fuse on the same circuit. Fusible links, while different in design, are identical in purpose and functionality. There are many different types of fuses, but most modern cars and trucks use one or more of the following types of bladed fuses, in descending order of size: Maxi (APX) heavy duty fusesThe largest type of blade fuse.Used in heavy duty applications.Available with higher amperage ratings than other blade fuses.Regular (ATO, ATC, APR, ATS) fusesThe first and standard type of blade fuse.Several different alternate versions that all fit in the same slots.Found in most modern cars and trucks.MiniSmaller than regular blade fuses, but available across a similar amperage range.Also available in a low-profile mini version.MicroThe smallest type of blade fuse.Available across the smallest range of amperage ratings.Comes in two versions: two prong micro2 and three prong micro3. Aren't All Car Fuses the Same? Modern car fuses are all based on the standard ATO and ATC “blade type” fuses that Littelfuse patented in the 1970s. There are multiple sizes and configurations of blade fuses today, but they all bear a physical resemblance to the original ATO fuses, and many applications still use standard ATO and ATC fuses. The differences between these various types of blade fuses are primarily size and number of terminals, although physically larger fuses are usually used in higher current applications. Older vehicles used a variety of different types of fuses, although the most common were “glass tube” fuses and “Bosch type” fuses, which can still be found today in older vehicles that are still on the road. Glass tube fuses consist of a glass tube, capped by metal terminals, and with a metal strip passing through the center. Bosch type fuses are also roughly cylindrical, but they are made of a solid ceramic material with a metal strip on the surface. Since automotive fuses are differentiated both by design type and current rating, all fuses most emphatically are not the same. Although it is definitely possible to replace any ATO fuse with any other ATO fuse, doing so can be extremely dangerous if the wrong amperage fuse is substituted. Similarly, it is sometimes physically possible to replace a Bosch type fuse with an American-style glass tube type, but sticking to the same amperage rating is imperative, and a flat-capped glass tube fuse will typically not fit well into a fuse holder designed for conical end caps. Types of Blade Fuses There are six types of blade fuses that you may run into when you pop open the fuse box on a modern car or truck: micro2, micro3, low-profile mini, mini, regular and maxi. For all blade fuses, the housing may be opaque or clear. When the housing is clear, it's usually easy to tell whether the fuse is bad, since the winding metal strip that connects the two terminals is easily visible. If the strip is broken, that means the fuse has blown. Micro2 fuses are the smallest type of blade fuse, and they are easily identifiable by the fact that they are so much taller than they are wide. In terms of size, low-profile mini fuses and regular mini fuses share the same body height and width, but the spade terminals of low-profile mini fuses barely extend past the bottom of the body. Micro3 fuses are larger than Micro2, low-profile, or mini fuses, but they are most easily identifiable by the fact that they utilize three spade terminals. Every other type of blade fuse only uses two terminals. They also include two fuse elements, which allows a single fuse to effectively handle two circuits. ATO and ATC fuses, or “regular” blade fuses, are the original and also the second largest type. Although many applications started to replace ATO and ATC fuses with mini fuses in the 1990s, they are still widespread. These fuses are wider than they are tall, and they come in two main types. ATO fuses are open at the bottom, while ATC fuses feature a plastic body that is totally enclosed. The largest type of blade-style fuse is the maxi fuse. These are significantly larger than any other type of blade or spade automotive fuse, and they are typically used for higher current applications. Automotive Fuse Color Coding While it’s possible to replace any ATC fuse with any other ATC fuse, any mini fuse with any other mini fuse, and so on, doing so is not safe if you don’t match the current ratings. Although fuses can blow under normal operating conditions, due to age and wear, a blown fuse often indicates a deeper problem. So if you replace a blown fuse with another fuse with a higher amperage rating, you may prevent the fuse from blowing again immediately, but you also risk damaging some other electrical component, or even starting a fire. There are three different ways to tell the amperage of a blade-type fuse. The first is to look at the top of the fuse, where you will find the amperage rating printed on or stamped into the plastic. If the rating has worn off, you can also look at the color of the fuse body or check the fuse diagram to see what type of fuse belongs in that particular slot. Colors and physical dimensions for blade type fuses are laid out in DIN 72581, and not all colors or amperage ratings are available in all sizes. Color Current Micro2 Mini Regular Maxi Dark blue 0.5 A No No Yes No Black 1 A No No Yes No Gray 2 A No Yes Yes No Violet 3 A No Yes Yes No Pink 4 A No Yes Yes No Tan 5 A Yes Yes Yes No Brown 7.5 A Yes Yes Yes No Red 10 A Yes Yes Yes No Blue 15 A Yes Yes Yes No Yellow 20 A Yes Yes Yes Yes Clear 25 A Yes Yes Yes Gray Green 30 A Yes Yes Yes Yes Blue-green 35 A No Yes Yes Brown Orange 40 A No Yes Yes Yes Red 50 A No No No Yes Blue 60 A No No No Yes Amber/tan 70 A No No No Yes Clear 80 A No No No Yes Violet 100 A No No No Yes Purple 120 A No No No Yes While color coding is standard almost across the board for different types of automotive blade fuses, two notable exceptions are 25 A and 35 A maxi fuses. These fuses are gray and brown, respectively, which are colors that are also used for lower amperage fuses. However, maxi fuses are not available in 2 A or 7.5 A, which are the ratings used by those colors, so there is no possibility of confusion. So What About Fusible Links? Fusible links perform the same basic function as fuses, but they go about it in a slightly different way. In automotive applications, a fusible link is a length of wire that is several gauges thinner than the wire that it is designed to protect. When all goes well, this results in the fusible link failing, and breaking the circuit, before the protected wiring can fail. In addition to simply being thinner than the rest of the wire in a circuit, fusible links are also encased in special materials that are designed to not catch on fire when exposed to high temperatures. So while extremely high current in a regular wire may cause a fire, a blown fusible link is less likely to do so. Fusible links can be found in a variety of places in cars and truck, but they are commonly used in high-amperage applications like starter motors, which can draw hundreds of amps. When this type of fusible link blows, the vehicle will no longer start, but the risks of fire are lessened. In other applications, the fusible link may be easier to get at and replace than the wiring it is designed to protect. Replacing Fuses and Fusible Links Replacing fuses is a relatively easy job that just about anyone can do, but it’s still important to take the time to make sure you replace them with the correct style and amperage rating replacement. Blade fuses are sometimes physically difficult to pull out, but most vehicles come with a fuse-puller tool that is located inside one of the fuse boxes or attached to a fuse box lid. Although it is fairly easy for a practiced eye to identify car fuses on sight, you can also look at a visual guide to help determine which type of fuse you need to obtain. If you replace a fuse, and you find that it blows again, that usually means there is some underlying problem that you will have to deal with. Replacing the fuse with a higher amperage fuse may seem to fix the problem temporarily, but identifying the components present on that circuit, and tracking down and fixing the actual, underlying problem, is the safer way to go. Replacing fusible links is often a more involved job than simply pulling a fuse, since they are typically bolted in place and are sometimes difficult to reach. It is a job that you can do at home if you have the right tools and are able to physically locate the blown fusible link, but it’s extremely important to use the correct replacement. In the same way that using a replacement fuse with the wrong amperage rating is a bad idea, replacing a blown fusible link with the the wrong part is extremely dangerous. In a best case scenario, the fusible link won't be able to handle the amperage of the application, and it will fail immediately. In a worst case scenario, you could end up with a fire. Under absolutely no circumstance should you ever replace a fusible link with an electrical cable. Maybe you have a ground strap or battery cable laying around that looks the right size and length, but don't even think about it. Call your local parts store, give them the application, and they'll be able to come up with a fusible link that's designed for the application that you're working with. Since fusible links often carry tremendous amounts of current, doing the job poorly, or using just any old replacement wire or cable, can result in a fire or a much more costly repair when other wiring fails later on. Continue Reading What Causes a Cigarette Lighter Fuse to Keep Blowing? Car Interior Lights Not Working? Don't Stay Stuck in the Dark! Does Your Amp Need a Fuse? Don't Smoke? You Can Replace a Cigarette Lighter With USB Four Ways a Car Amplifier Fuse Can Blow Gauges in Your Car Not Working? Try These Fixes Car Windows Stuck? Here's How to Fix Them Headlights Not Working? Try These Fixes Can Cigarette Lighter Heaters Actually Work? Five Signs of a Dead Car Battery What to Do When Your Electrical System Shuts Down These Car Heater Alternatives Actually Work Why Your Car Won't Start Even Though the Lights Work Troubleshooting a Broken Head Unit Install a Power Inverter in Your Car or Truck What Can Cause a Car Stereo to Only Works Sometimes?