A Guide To Automotive Fuses

What are Automotive Fuses?

Automotive fuses are used to protect the wiring and electrical equipment for vehicles. There are several different types of automotive fuses and their usage is dependent upon the specific application, voltage, and current demands of the electrical circuit. Automotive fuses can be mounted in fuse blocks, inline fuse holders, or fuse clips. Some automotive fuses are occasionally used in non-automotive electrical applications. Standards for automotive fuses are published by SAE International (formerly known as the Society of Automotive Engineers).

Automotive fuses can be classified into four distinct categories:

• • Blade fuses
  • Glass tube or Bosch type
  • Fusible links
  • Fuse limiters

Blade Fuses

Blade fuses (also called spade or plug-in fuses), with a plastic body and two prongs that fit into sockets, are mostly used in automobiles. Another common usage is in equipment with comparatively simple, low voltage DC electrical systems such as towed campers and marine applications such as sailboats and motor boats (typically smaller cabin cruisers).Each fuse is printed with the rated current in amperes on the top.

Size Groups

Blade size	Blade group	Dimensions L × W × H	Common ratings (maximum current)
Micro2	APT, ATR	9.1 × 3.8 × 15.3 mm	5, 7.5, 10, 15, 20, 25, 30
Micro3	ATL	14.4 × 4.2 × 18.1 mm	5, 7.5, 10, 15
Low-profile mini	APS, ATT	10.9 × 3.81 × 8.73 mm	2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30
Mini	APM, ATM	10.9 × 3.6 × 16.3 mm	2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30
ATO(regular)	APR, ATC, ATO, ATS	19.1 × 5.1 × 18.5 mm	0.5, 1, 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30, 35, 40
Maxi	APX	29.2 × 8.5 × 34.3 mm	20, 25, 30, 35, 40, 50, 60, 70, 80, 100, 120

Glass Tube

North-American built automobiles up to at least 1986 had electrical systems protected by cylindrical glass cartridge fuses rated 32 volts DC and current ratings from 4 amperes to 30 amperes. These are known as “SFE” fuses, as they were designed by the Society of Fuse Engineers to prevent the insertion of a grossly inadequate or unsafe fuse into the vehicle’s fuse panel. These SFE fuses all have a 1⁄4 inch diameter, and the length varies according to the rating of the fuse.

SFE – These are the original glass fuses for automotive use. SFE stands for Society of Fuse Engineers and has different lengths so that the wrong fuse cannot be installed into the wrong placement. They are ¼” in diameter, from 5/8″ up to 1 7/16″ long.

Outside of SFE fuses are AG type, which stands for Automotive Glass with a suffix letter to note the type.

Type	Physical Size
AGA (1 to 30 amp)	1/4” diameter x 5/8” long
AGB	0.177” diameter x 0.588” long
AGC (0.125 to 50 amp)	1/4 diameter x 1-1/4” long
AGS	9/32” diameter x 1-1/4” long
AGU (1 to 60 amp)	13/32 diameter x 1-1/2” long (sometimes referred to as Midget fuses)
AGW (1 to 30 amp)	1/4” diameter x 7/8” long
AGX (1 to 30 amp)	1/4” diameter x 1” long
AGY (50 amp only)	1/4” diameter x 1 7/16” long
UK (35 to 50 amp)	1/4” diameter x 1 1/4” long

Bosch type

Bosch type fuses (continental, torpedo, European, or GBC-type fuses) are used in old (often European) automobiles. The physical dimension of this type of fuse is 6×25 mm with conical ends. Bosch type fuses usually use the same color coding for the rated current. The DIN standard is 72581/1.

Color	Current rating
Yellow	5 A
White	8 A
Red	16 A
Blue	25 A
Grey	40 A

Fusible links

A fusible link is a mechanical or electrical safety device. They are used in fire sprinkler heads to activate the sprinkler in the presence of heat. They are used in automotive electrical systems as a fuse.

Fuse Limiters

Limiter fuses consist of a metal strip for currents over 10 amperes. Also referred to as Current Limiting Fuses, they feature an internal fuse element that melts when the current passing through the fuse element is within the specified current limiting range of the fuse. As the fuse element melts, it creates a high resistance to reduce the magnitude and duration of the current flowing through the fuse to protect the electrical circuit and connected equipment. Frequently, these are used near starter battery fuse boxes. They are also used in electric vehicles, e.g., in forklift trucks. Because strip fuses require the use of tools for replacement they are therefore legally considered non-serviceable components for end-users.

How to tell if automotive fuses are blown?

The best way to identify a bad fuse is when an electrical component suddenly stops working. In most cases, this may be like the dashboard light goes out soon, the stereo stops working, and so on. When too much current passes through a specific circuit, the fuse of your car will break. The fuse is blown to avoid fire or serious damage to your car. So once you find a car fuse burned out, you must find it and get a car fuse replaced.

How to replace automotive fuses?

Use the following steps to learn how to easily replace a car fuse:

1. Disconnect the car battery

Before opening the fuse box or starting the work of the fuse box, make sure to turn off the ignition device of the vehicle and disconnect the battery.

2. Find the fuse box

In most cases, you can find the car fuse box under the hood or near the dashboard. If you have any questions, you’d better check the manual. It will have the exact location of the car fuse box. After finding the car fuse box, remove the lower panel cover.

3. Find out the broken fuse

You can find many fuses of different colors once you remove the cover. The colors and numbers on the fuse represent different amperes. The chart on the back of the cover usually shows the power rating of each fuse. It is easy to find a broken fuse because it will have a broken filament or look black inside. Use a flashlight to quickly locate.

4. Remove the broken fuse.

The broken fuse can be removed by hand or with some tools. A car fuse puller or pincer is the best tool to remove damaged fuses. Remember, it is more difficult to remove a broken fuse than a working fuse. So be careful if you want to remove it manually.

5. Replace the fuse with a new one.

Be careful when you insert a new fuse into the fuse box. This step can only be performed after consulting the owner’s manual. Confirm that the replaced fuse has the same amperage as the removed fuse. You can insert the new fuse into the position of the removed fuse by hand. Please note that inserting a wrong current fuse will cause serious electrical problems.

6. Turn on the ignition device.

Turn on the ignition switch and check whether the circuit that bothers you works normally. If so, you have successfully replaced the car fuse. However, if the new fuse breaks as soon as it is installed, you should know that there is a problem with the circuit. Then, quickly visit a mechanic or make an appointment with the dealer to solve the problem.

How to replace automotive fuses: some necessary skills

• Realize that the car fuse has blown when the electrical components stop working.
• When replacing the fuse, you can find the fuse box under the hood or near the instrument panel.
• Fuses have different colors and numbers that represent their ampere rating. A broken fuse will have broken wires, or it looks black inside.
• You can remove the burnt fuse by hand. Or use an automobile fuse removal tool, such as an automobile fuse pull or needle pliers to remove it. Use a multimeter to test the fuse instead of taking it out of the box.
• Ensure that the replaced fuse has the same amperage as the removed fuse. Inserting a fuse with incorrect current can cause severe electrical problems.
• The fuse may burn out at any time. Therefore, be sure to put the spare fuse in the glove box of the car. In addition, there is a fuse pulling tool in the car always. In addition, when the fuse blows out, make sure to check its circuit to find out the cause of damage.