Automotive fuses are not unlike any other fuse on today’s marketplace. They are of course, although, engineered for lower voltages. Different auto manufacturers use certain types of fuse block configurations for their products depending on type, size and year of their applications. No matter what the connection design, the purpose is to protect components and circuits from excessive current. If you think of a circuit with components as a chain, the fuse would be the weakest link.
Pictured above is the blade type fuse that was (and is still) one of the most popular style of fuses in the automotive market. Fuse manufacturers were intelligent enough to color code them for ease of identification.
Pictured above are several “mini blade” fuses which are also very popular in the automotive electrical marketplace.
The glass tube style fuse is vested in automotive history forever in the “classics” and “antiques”.
Most fuse manufacturers have adapted a standard colorization format.
Dark Blue .5 amp
Black 1 amp
Gray 2 amp
Violet 3 ampes
Pink 4 amp
Tan 5 amp
Brown 7.5 amp
Red 10 amp
Blue 15 amp
Yellow 20 amp
Clear 25 amp
Green 30 amp
Blue Green 35 amp
Orange 40 amp
Red 50 amp
By doing this basic color code, manufacturers enabled the consumer to quickly identify how many amps a fuse is rated at, both on the car and in the store before purchasing. Fuses are sold in small quantities all the same color or as various colors in a standard “variety” pack.
Tech Explanations on Fuses and Fuse (Fusible) Links
The rated voltage of a fuse link has to be at least equal or higher than the operating voltage of the device or assembly unit which is to be protected with the fuse link. If the operating voltage is very low, the fuse link’s natural resistance (voltage drop) must possibly be taken into consideration.
The voltage drop is measured according to standard all other standard voltage drop methods. The rated current of a fuse link should approximately correspond to the operating current of the device or assembly unit which is to be protected.
Higher ambient temperatures mean additional load for the fuse links. The heating conditions of the maximum occurring ambient temperature have to be checked, in particular with high rated currents of the fuses, and a strong thermal radiation of components nearby. For such applications, the fuse should be derated.Due to different specifications of rated current the recommended continuous current of the fuse links is max. 80% of their rated current (with an ambient temperature of 23°C)
The melting integral parts results from the melting current and the corresponding melting time. At excess current with melting times < 5 ms the melting integral remains constant. The melting integral is an index for the time-current characteristic and informs about the pulse consistency of a fuse link.
The breaking capacity should be sufficient for many operating and error conditions. The short-circuit current (maximum fault current) to be interrupted by the fuse links at the rated voltage under default conditions must not be higher than the current corresponding to the breaking capacity of the fuse link.
The common fuse has been around since the times of Thomas Edison. The earliest use of fuses was to protect the first telegraph stations from lightning strikes. The most magical note about fuses is this: Just imagine how many lives have been saved and how many properties have been spared by such a simple, inexpensive, easy to install device.