It is necessary to replace the blown fuse and after switching on the consumer, check whether the fuse will burn out again immediately. In this case, the defect must first be identified and eliminated, as a rule, we are talking about a short circuit. This means that in some place, including inside some electrical device, the ground and plus are connected.
Second step of checking: If the indicator lamp does not light or the motor does not work even though the fuse is good, you should check the supply voltage.
Checking the lamps
Remove the lamp and inspect it. If the filament is burnt out or the glass bulb is loose on the base, replace the lamp.
To accurately determine that the lamp is not defective, proceed as follows: Connect the lamp via wires directly to the battery. In this case, the polarity of the wires connected to the lamp is not important. If the lamp does not light, replace the lamp.
Note: Make sure that the wire contacts and the lamp socket are not corroded. If so, clean the contacts.
If the lamp is OK, insert the lamp and turn it on. If the lamp does not light, check the power supply with a tester. To do this, connect the tester to the ground. This means: The tester wire must be connected to a reliable ground (bare metal) or directly to the negative terminal of the battery. Hold the test needle of the tester (+) either on the current-supplying contact of the connector or pierce the current-supplying wire with it. If the tester lights up but the lamp does not light, there is a break in the ground wire of the lamp. To check this, apply the ground using an auxiliary wire to the lamp socket. The lamp should light.
Note: There are lamps that only have a current-carrying wiring, such as parking light lamps, interior lighting. These lamps are connected to the vehicle's ground directly through their housing.
If there is no voltage in the lamp's current-supply wire, i.e. the tester does not light, it is very likely that the switch has failed. Ring the switch.
Checking Electric Motors
In cars, more and more service functions are taken over by small electric motors.
Each motor is switched on by a switch, usually manually, when needed. The electric antenna is switched off automatically by the radio receiver.
Check the fuse of the corresponding electric motor and replace if necessary.
Note: The electric motors of the electric window lift and sunroof have automatic fuses that switch off in the event of overload and switch on again after a while. Before switching on again, the cause of the overload must be eliminated. This may be frozen glass or dirty window guides.
If the fuse blows again, the cause is a short circuit.
To clearly determine that there is a motor defect, connect the motor with 2 wires (0 about 2 mm) directly to the battery. The positive wire to the positive terminal, the negative wire to the negative terminal of the motor. The location of the terminals in case of doubt is given in the electrical diagrams. In addition, the motor can be removed for inspection. All motors of the car are powered by the on-board network (12-14 V). If the motor works normally, the reason was in the power supply.
Note: Slow and jerky rotation of the motor indicates worn carbon brushes. In this case, the brushes should be replaced.
If the engine is running, use the electrical diagram to determine which wire supplies power when the switch is turned on and before that the ignition is turned on.
Check the current-supplying wire with a tester. Since electric motors consume a lot of current, you can use a regular aiming lamp as a tester, which has a sharp needle at the end of the wire, which can be used to pierce the wire. This is a simple way to check the voltage. Motors that have reverse rotation, such as window lift motors, have two positive connection terminals.
Note: For checking the wiper motor, see the relevant section.
If there is no voltage at the motor terminals, the cause is in the power supply. Find the defect using the electrical circuit and fix it. Due to the high current consumption, motors are often switched on via intermediate relays. For checking the relay, see the corresponding section.
If no defect is found, check the switch.
If the wire is defective, it is more reasonable to lay a new wire, since it is difficult to find the exact location of the wire defect.