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 type
Blade 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,
mini regular
maxi 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 voltage 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. = Size groups=
Where space permits, a miniature circuit breaker is sometimes used to replace a
blade-type fuse in the same fuse holder. = Color coding=
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. Regular fuses rated 0.5 A, 35 A and 40 A
are not mentioned in the DIN standards, but are available in some products from
Littelfuse, among others. Bosch type
Bosch type fuses are used in old 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. = Color coding=
Lucas type 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" [~29.4 mm] long, while the US standard
1/4" glass tube fuse is 1 and 1/4" [~32.0 mm] long.
= Color coding= Glass tube type
North-American built automobiles up to 1981 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 was 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.
A 4 amp SFE 4 fuse is 5⁄8 inch long, a 6 amp SFE 6 fuse is 3⁄4 inch long,
a 7.5 amp SFE 7.5 fuse is 7⁄8 inch long, a 9 amp SFE 9 fuse is 7⁄8 inch long,
a 14 amp SFE 14 fuse is 11⁄16 inch long, a 20 amp SFE 20 fuse is 11⁄4 inch long,
and a 30 amp SFE 30 fuse is 17⁄16 inches
long. There are a number of lookalike fuses
which can easily be confused with these. In general this type of fuse will have
an "AG" label of some kind, which originally stood for "all glass." There
are at least seven different sizes of fuses with a 1/4 inch diameter. The
fuses listed are the most common for the size, which is always a fast-acting
fuse: 1AG size, type AGA, 1 amp to 30 amp, 1/4
inch diameter by 5⁄8 inch long 7AG size, type AGW, 1 amp to 30 amp, 1/4
inch diameter by 7⁄8 inch long 8AG size, type AGX, 1 amp to 30 amp, 1/4
inch diameter by 1 inch long 3AG size, type AGC, 0.125 amp to 50 amp,
1/4 inch diameter by 11⁄4 inch long UK size, type UK, 35 amp to 50 amp, 1/4
inch diameter by 11⁄4 inch long 9AG size, type AGY, 50 amp, 1/4 inch
diameter by 17⁄16 inch long 5AG size, type AGU, 1 amp to 60 amp,
13⁄32 inch diameter by 11⁄2 inch long. Also called "Midget fuses."
These and other fuses are still being manufactured for many applications,
including for AC circuits and DC uses. Some are time delayed, slow reacting, or
have leads for terminals used in circuits without a fuse holder. Many of
the fuse dimensions and characteristics are published by the Society of
Automotive Engineers as Standard SAE J 554.
Limiter type 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. See also
Fusible link References
External links Automotive Fuse Selection Guides
Cooper Bussmann - Automotive Selection Guide For Vehicles Of Years 1990–2007
Blade Fuses Littelfuse Blade Fuses: Micro2, Micro3,
Low Profile Mini, Mini, Regular, Maxi Cooper Bussmann - Automotive Blade Fuses
OptiFuse - Automotive Blade Fuses Fusible Links
Cooper Bussmann - Automotive High-Amp Fuses and Fusible Links
Glass Tube Fuses Cooper Bussmann - Glass and Ceramic Tube
Fuses