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Automotive fuses are a class of fuses used to protect the wiring and electrical equipment for vehicles. They are generally rated for circuits no higher than 24 volts direct current, but some types are rated for 42-volt electrical systems. They are occasionally used in non-automotive electrical products.
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. Each fuse is printed with the rated current in amperes on the top. These types of fuses come in six different physical dimensions:
- micro2, micro3, low-profile mini (APS),
- mini (APM / ATM)
- regular (APR / ATC / ATO)
- maxi (APX) heavy-duty.
Unofficially, the APS fuse is sometimes called "micro" since the term means smaller than mini, but recently fuses using the micro name have been released. Regular blade-type fuses, also known as standard fuses, were developed in 1976 for low-voltages use in motor vehicles. The mini fuses were developed in the 1990s. Blade type fuses can be mounted in fuse blocks, in-line fuse holders, or fuse clips. The ATC fuse has a fuse element that is closed or sealed inside the plastic housing and the ATO fuse has a fuse element that is open or exposed on the bottom of the fuse between the blades.
|Blade Size||Blade Group||Dimensions L × W × H||Common Ratings|
|Micro2||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|
|Regular||APR, ATC (Closed), ATO (open)||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|
Where space permits, a miniature circuit breaker is sometimes used to replace a blade-type fuse in the same fuse holder.
Blade fuses use a common coloring scheme for the micro2, micro3, low-profile mini, mini, and regular size fuses, and a partial color similarity with the maxi size fuses. The following table shows the commonly available fuses for each size group.
|Dark blue||0.5 A|
Bosch type fuses (also known as torpedo, ATS, 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. The size of the fuse is: 6×25 mm.
Lucas type fuses are used in old British-made or assembled automobiles. The physical length of this ceramic type of fuse is either 1 inch or 1.25 inch, with conical ends. Glass tube fuses have straight ends. Lucas type fuses usually use the same color-coding for the rated current. Lucas fuses have three ratings; the continuous current they are designed to carry, the instantaneous current at which they will fuse, and the continuous current at which they will also fuse. The figure found on Lucas fuses is the continuous fusing current which is twice the continuous ampere rating that the system should be using; this can be a source of confusion when replacing Lucas fuses with non Lucas fuses. The Lucas 1/4" diameter glass tube fuse have a different physical length as compared to the standard US item. The Lucas 1/4" diameter glass tube fuse is 1 and 5/32" [~29.4mm] long, while the US standard 1/4" glass tube fuse is 1 and 1/4" [~32.0mm] long.
|Color||Continuous ampere (=Rated Current)||Instantaneous fusing ampere||Continuous fusing ampere|
|Red on Yellow||2.5||6||5|
|Red on Green||5||12||10|
|Green on Black||5||12||10|
|Red on Brown||6||14||12|
|Purple on Yellow||25||60||50|
|Yellow on Red||30||75||60|
Glass tube type
North-American built automobiles up to 1981 had electrical systems protected by glass cartridge fuses rated 32 volts and current ratings from 4 amperes to 30 amperes. The fuse dimensions and characteristics are standardized by the Society of Automotive Engineers standard J554. All fuses are 1/4 inch diameter, and the length varies according to the rating of the fuse. A 4 amp fuse is 5/8 of an inch long, a 20 amp fuse is 11⁄4 inches long, and a 30 amp fuse is 17⁄16 inches long.
Limiter fuses consist of a metal strip from a lock plate, for currents over 40 amperes. Frequently, these are used in close proximity to starter battery fuse boxes. They are used also 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.
- Automotive Fuse Selection Guides
- Blade Fuses
- Littelfuse Blade Fuses: Micro2, Micro3, Low Profile Mini, Mini, Regular, Maxi
- Cooper Bussmann - Automotive Blade Fuses
- OptiFuse - Automotive Blade Fuses
- Fusible Links
- Glass Tube Fuses