This text is machine translated.
In motor vehicles, as electrical power sources, there is the battery and the alternator, and on the other hand there are loads of electrical energy in the form of lamps, electrical and electronic systems connected via individual circuits. In the event of overload or short circuits, sensitive and dangerous faults can also occur in other systems within the vehicle or even a fire can be triggered. To prevent this, fuses are installed in the vehicle's circuits.
About car fuses
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What types of car fuses are there and how do they work?
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What practical versions of car fuses are available and how are they specified?
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Dimensions and nominal currents of the car blade-type fuse fuses
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Color coding of the car blade-type fuse
What types of car fuses are there and how do they work?
CAR fuses in torpedo form were common until the early 1980er.
As in other areas of electrical engineering, electric circuits are protected against overload due to excessive currents in the motor vehicle by interrupting the current flow. In the simplest case, this is done by means of a fuse consisting of a fuse element. This is a small piece of metallic conductor with a defined, low resistance. If the current flows through it, it heats up. The metal and its mechanical dimensions are selected in such a way that it melts when a defined current value is exceeded for a longer period of time and thus interrupts the circuit. The second option is thermally triggered switches. Here, a bimetal is heated by the flowing current. If this exceeds a specified value, the bends and the current flow is mechanically interrupted by the switch. This type of fuse is also known as "Automat". In contrast to fusible links, which are unusable after tripping and must be replaced, automatic machines can be switched on again after cooling down and correcting the cause of the overload.
What practical versions of car fuses are available and how are they specified?
Because electrical functional units in conventional motor vehicles (except electric cars!) Only with low voltages below 50 volts, typically 12 V or 24 V, can they be kept quite small. Due to the low voltage, however, the currents to be protected can be much higher than those in domestic installations.
Until the 1980er, melting inserts in the so-called "torpedo form" were used in older cars. Here, a metal strip is located on a small insulating body, which runs pointedly on both sides, which represents the actual melting element. At the ends are the contact surfaces to which the fuse in the fuse holder is connected to the circuit.
Modern cars are equipped with blade-type fuses, which are standardized according to ISO 8820-3. Here, the metallic conductor of the melting element is connected with two flat-blade terminals and installed in a flat plastic housing. Blade-type fuse types are available in different sizes: Mini, standard and maxi. These differ in the dimensions and the selection of the respective nominal currents.
Standard blade-type fuse protection is common in today's motor vehicles.
Dimensions and nominal currents of the car blade-type fuse fuses
| Model | Dimensions L x W x H | Nominal current A |
|---|---|---|
| Mini fuse (FK1) | 10.9 × 3.6 × 16.3 mm³ | 2; 3; 4; 5; 7.5; 10; 15; 20; 25; 30 |
| Standard fuse (FK2) | 19.1 × 5.1 × 18.5 mm³ | 1; 2; 3; 4; 5; 7.5; 10; 15; 20; 25; 30; 35; 40 |
| Maxi-plug fuse (FK3) | 29.2 × 8.5 × 34.3 mm³ | 20; 25; 30; 35; 40; 50; 60; 70; 80; 100 |
The fuse holders are located in the car, for example, under the dashboard in places that are difficult to reach and see. Because the plug-in fuses have the same dimensions for different nominal currents, fuses with incorrect values could be used inadvertently. To avoid confusion, the plastic enclosures are colored, with one color assigned to each rated current.
Color coding of the car blade-type fuse
Black
1 Ampere
Grey
2 Amps
Purple
3 Ampere).
pink
4 Amps
Light brown
5 Amps
brown
7.5 Ampere
Red
10 Amps
Blue
15 Amps
Yellow
20 Amps
Matt
25 Amps
Green
30 Amps
blue-green
35 Amps
Orange
40 Amps
Red
50 Amps
Blue
60 Amps
Light brown
70 Amps
Clear
80 Amps
Purple
100 Amps
Automatic fuses are available in the dimensions of the mini and standard flat fuses. Due to the more complex switching mechanism, the machines are slightly higher than the corresponding melting inserts.
What was to be observed when selecting and using car fuses in the car?
In order for fuses to effectively protect the electrical systems in a car against overload and damage, only the types specified in the vehicle's operating instructions with the same nominal current values may be used as replacements. First, the cause that caused the fuse to trip must be determined and eliminated. This can be, for example Short circuits are caused by worn cables or defective consumers. If fuses are triggered repeatedly, the error has not yet been corrected. The use of fuses with higher rated currents is not a permissible solution in such a case, because this can cause major consequential damage, which may also lead to the loss of warranty claims.
Older car fuses, especially torpedo types, tend to corrode their contact surfaces. Due to the low voltages and at the same time high currents, significant voltage drops can occur here. In the event of faults in the electrical and electronic systems of a car, the contacts of the fuses should therefore also be checked. If corrosion is visible here, they must be replaced.
The replacement of flat fuses is often not easy because they are arranged in close proximity to each other in the fuse boxes. The fuses are difficult to grasp with your fingers. For ease of use, there are practical fuse screwdrivers that make it easy to grasp and pull out the fuses.
The fuse puller makes it easier to replace flat fuses.
A larger number of fuses with different nominal currents are installed in a car. In order to be prepared for all possible faults, it is recommended to have a range of fuses available. For this purpose, appropriate sets are available in assortment boxes for the most important types, so that a suitable fuse is always available in the event of a fault.