Car guards are gatekeepers and bodyguards peace automotive electronics . Whenever a sudden short circuit or surge threatens any of the delicate electronics found in modern cars and trucks, the fuse is ready to bravely throw itself into the field of fire.
In this case, the fuse uses a shaped bullet for a more valuable, complex or irreplaceable component or device, such as 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 is usually revealed by repeated fuse failures in the same circuit.
Fusible links, although 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 fuses, in order of size:
- Maxi (APX) Heavy Duty Fuses:
- The largest type of guard blade.
- Used in harsh environments.
- Available with higher amperage rating than other fuses.
- Conventional (ATO, ATC, APR, ATS) fuses:
- The first and standard type of fuse blade.
- Several different alternate versions that all fit into the same slots.
- Found in most modern cars and trucks.
- Mini:
- Smaller than conventional fuses but available in a similar amperage range.
- Also available in a low profile mini version.
- Micro:
- The smallest type of fuse blade.
- Available in the smallest current range.
- It comes in two versions: two-pin micro2 and three-pin micro3.
Aren’t all car fuses the same?
All modern automotive fuses are based on standard ATO and ATC fuses, which Littelfuse patented in the 1970s . There are many sizes and configurations of 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 different types of fuses are mainly in the size and number of terminals, although physically larger fuses are usually used in high current applications.
Older cars used various types of fuses, although the most common were the «glass tube» and «Bosch» fuses still found in older cars still on the road.
Glass tube fuses consist of a glass tube closed with metal terminals and with metal strip running through the center . Bosch type fuses are also roughly cylindrical, but they are made of a hard ceramic material with a metal strip on the surface.
Because automotive fuses vary in both construction type and amperage, all fuses vary the most from one another. While it is entirely possible to replace any ATO fuse with any other ATO fuse, it can be extremely dangerous if the wrong current fuse is replaced.
Similarly, it is sometimes physically possible to replace a Bosch-style fuse with an American-style glass tube type, but it is imperative to stick to the same amperage rating, and a flat glass tube fuse is not usually suitable for a fuse holder designed for tapered plugs.
Blade fuse types
There are six types of blade fuses that you may encounter when you open the fuse box on a modern car or truck: micro2, micro3, low profile mini, mini, regular, and maxi.
For all fuses, the body can be opaque or transparent. When the case is loose, it’s usually easy to tell if a fuse is a bad one, as the winding metal strip connecting the two terminals is clearly visible. If the strip is broken, then the fuse is blown.
Micro2 fuses are the smallest type of blade fuses and are easy to identify by being much taller than they are wide. Low profile mini fuses and regular mini fuses are the same body height and width in size, but the blade terminals of low profile mini fuses barely extend beyond the bottom of the body.
Micro3 fuses are larger than Micro2, low profile or mini fuses, but they are the easiest to identify by the fact that they use three spade terminals. Any other type of fuse uses only two terminals. They also include two fuse elements which allows one fuse to effectively handle two circuits.
ATO and ATC fuses, or «regular» fuses, are the original and also the second largest type. Although many applications began to replace ATO and ATC fuses with mini fuses in the 1990s, they are still widely used. 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 have a fully enclosed plastic case.
The largest type of blade fuse is the Maxi fuse. They are significantly larger than any other type of blade or spade automotive fuse and they are generally used for higher current applications.
Automotive fuse color coding
While it is possible to replace any ATC fuse with any other ATC fuse, any mini fuse with any other mini fuse, etc., it is not safe to do so unless you are within the current settings. While fuses can blow under normal operating conditions due to age and wear and tear, a blown fuse often indicates a more serious problem.
So if you replace a blown fuse with another fuse with a higher current rating, you may prevent the fuse from blowing again immediately, but you also risk damaging some other electrical components or even starting a fire.
There are three different ways to determine the amperage of a blade fuse. First, look at the top of the fuse, where you will find the amperage rating printed on the plate or stamped. If the rating has degraded, you can also look at the color of the fuse body or check the fuse diagram to see what type of fuse is in that particular socket.
Colors and physical dimensions for blade type fuses are specified in the standard DIN 72581 and not all colors and amps 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 |
|
Grey |
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 |
Grey |
|
green |
30 A |
Yes |
Yes |
Yes |
Yes |
|
Aquamarine |
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 on almost all types of automotive blade fuses, two notable exceptions are the 25A and 35A maximum fuses. These fuses are gray and brown, respectively, which are also used for lower amperage fuses. However, maximum fuses are not available in 2A or 7.5A, which are the ratings used by these colors, so there is no confusion.
So what about fusible links?
Fuses perform the same basic function as fuses, but perform them in a slightly different way. In automotive applications, a fusible link is the length of wire that is several measurements thinner, than the wire it is intended to protect. When all goes well, this causes the fuse link to fail and break the circuit before the protective wiring can fail.
In addition to being simply thinner than the rest of the wire in the circuit, fusible links are also encased in special materials designed to prevent fire when exposed to high temperatures. So while an excessively high current in a normal wire can cause a fire, a blown fusible link is less likely to occur.
Fuse links can be found in a wide variety of places in cars and trucks, but they are typically used in high current applications, such as starting motors which can consume hundreds of amps. When this type of fusible link blows, the car will no longer start, but the risk of fire is reduced. In other applications, the fusible link is easier to remove and replace than the wiring it is designed to protect.