Logo carsalmanac.com

What's the problem if a fuse blows?

Table of contents:

What's the problem if a fuse blows?
What's the problem if a fuse blows?

If the fuse in the car constantly blows, this is a reason to start looking for a short circuit or overload cause in the electrical circuit. It is worth checking the operating modes of the engines: stove, washer, wipers. Often the currents become large when the headlights, dimensions are turned on.

Possible causes

The fuse blows - this means the overload protection is activated. It is worse if it is whole and the conductors are heated at the same time. There can be only one reason for such a deviation in the operation of fusible inserts - they set a higher rating than indicated in the electrical diagram.

blown heater fan fuse VAZ 2107

Fuse blows due to lower rating. All protective elements should be checked. Often car manufacturers list these values ​​near the installation site or on the plastic cover of the electrical box.

In the latest versions of cars, if the fuse blows, the on-board computer monitor displays the numbererrors. According to the manual, you can quickly determine the installation location of the faulty element. The unit is installed in the cabin for the convenience of replacing failed fuses.

It is often enough to replace a burned-out element, but if the fuse constantly blows, this requires finding and eliminating the cause. Leakage currents are a major problem in used cars. This situation occurs when the wiring is very worn.

Domestic cars

The "classic" of the automotive industry, the 2106, 2107, 2103 series had many weaknesses in electrical equipment. Connections from long years of operation weaken, and motors change conductivity. From vibrations and moisture, leakage currents appear on the case, the distribution of potentials changes.

A common problem on the "classic" is the formation of oxides on the contacts. However, this situation leads to an additional voltage drop, the fuse is unlikely to blow. More likely, it will fail due to poor contact.

Negative fuse ratings create troubleshooting problems. This is possible when the currents exceed the nominal ones slightly. The fusible element is constantly heated to a temperature that is not enough for its combustion.

Problem in the heating system

If the fuse of the VAZ-2107 stove fan blows, then you should first look for the reasons in the engine itself. The impeller is often clogged with dust, pieces of dry leaves. Revision of rotating elements will not hurt.

fuse keeps blowing

Check supply contactsvoltage. They must be insulated and securely fastened. The engine cannot run if moisture gets inside. Between the rotating elements there is a gap in which there should be no foreign inclusions. Although it is sealed, moisture can get in under certain conditions.

A fuse may blow due to a faulty control circuit. It is worth checking the stove motor relay, connections to it, the integrity of the tracks on the circuit board. If you suspect a malfunction, you should replace the element, its cost is low compared to the price of the engine.

Problems in the cooling system

The radiator cooling fan consumes high currents, the slightest pollution of it increases the values ​​​​by more than 20% of the nominal. This is enough to warm up and subsequently blow the fuse. But more often this happens at the time of launch.

size fuse blows

The simultaneous inclusion of several powerful consumers on used cars often leads to the fact that the cooling fan fuse blows. VAZ 2107 is equipped with a limited power generator with voltage stabilization using one stabilizer. If the latter fails and produces excessive values, the system will be overloaded and the first loaded fusible element will burn out.

Faulty fan bearing will also lead to increased current values. A sparking contact in the enable relay leads to pulses in the motor windings. As a consequence, the fusible element is heated. Cleaning the closing contacts orreplacement of the relay itself is necessary.


If the size fuse blows, it indicates a short circuit in the lighting circuit. Lamps may not match in wattage after replacement. Rarely, but there are cases when a short circuit occurs inside a glass bulb. Although external inspection shows that the electrodes are connected.

fuse keeps blowing

Such a lamp must be replaced and the operation of the circuit checked without it. Fuses can be defective, designed for a different current. It is worth buying in the departments of auto shops elements of proven brands.

Violation of the tightness of the headlight leads to the fact that moisture accumulates in the cartridge where the lamp is installed. This can be determined by the fogging of the glass from the inside in the morning or late in the evening. Such a headlight must be replaced, on new cars this can be done under warranty.


First of all, the electric circuit "rings" on the case. In this case, the battery terminals are disconnected. It must be remembered that the second wire from the engine goes to the housing, it must have zero contact resistance. The supply conductor is subjected to a short circuit test.

blown fuse in the car

If the wiring is intact, proceed to check the voltages of the electrical circuit assembly. Measuring points are determined according to the diagram in the vehicle manual. Also, the power at the battery terminals must be at least 12 V with the engine off. When running, a value above 13.6 V is measured.

A multimeter can measure resistance, integritycontacts, check the voltage. The presence of oxides or mechanical damage is determined visually.

Popular topic