Be sure to replace the blown fuse and, after switching on the consumer, check whether the fuse does not immediately blow again. In this case, the defect must first be identified and eliminated, usually a short circuit. This means that in some place, including inside some electrical device, ground and plus are connected.
The second step of the test: If the control lamp does not light or the motor does not work with a good fuse, check the supply voltage.
Checking lamps
Remove the lamp and inspect it. If the filament is burnt out or if the glass bulb is dangling on the base, replace the lamp.
To accurately determine that the lamp has no defects, proceed as follows: Connect the lamp through the wires directly to the battery. In this case, the polarity of connecting the wires to the lamp is not important. If the lamp does not light up, replace the lamp.
Note: Make sure that the wire contacts and the lamp holder are not corroded. Otherwise, clean the contacts.
If the lamp is OK, insert the lamp and turn it on. If the lamp does not light up, check the power supply with a probe. To do this, connect the probe to ground. This means: The probe lead must be connected to a reliable ground (bare metal) or directly to the negative battery terminal. test needle (+) hold either on the current-carrying contact of the connector, or pierce the current-carrying wire with it. If at the same time the probe lights up, but the lamp does not burn, there is a break in the lamp ground wire. To check this, apply a ground with an auxiliary wire to the lamp socket. The lamp should light up.
Note: There are lamps that have only current-carrying wires, such as parking lights, interior lighting. These lamps are connected to the vehicle ground directly through their housing.
If there is no voltage in the lamp lead wire, and that is, the probe does not light up, the switch is very likely to fail. Ring the switch.
Checking electric motors
In the car, more and more service functions are taken over by small electric motors.
Each motor is turned on by a switch if necessary, most often manually. At the electric antenna, switching off is carried out automatically from the radio receiver.
Check the fuse of the relevant electric motor, replace if necessary.
Note: The electric motors for the power window and the sunroof are equipped with automatic fuses that switch off when overloaded and switch on again after a short period of time. The cause of the overload must be removed before restarting. It could be frozen glass or dirty window rails.
If the fuse blows again, the cause is a short circuit.
To unequivocally determine that there is a defect in the motor, Connect the motor with 2 wires (0 about 2 mm) directly with the battery. Positive wire to the positive terminal, negative wire to the negative terminal of the motor. The location of the terminals, in case of doubt, is shown in the wiring diagrams. In addition, the motor can be removed for inspection. All car motors are powered from the onboard network (12 -14 V). If the motor is running normally, the problem was in the power supply.
Note: Slow and jerky motor rotation indicates worn carbon brushes. In this case, the brushes should be replaced.
If the motor is running, determine from the wiring diagram which wire supplies power when the switch is turned on and before that the ignition is turned on.
Check the lead wire with a probe. Since electric motors consume a lot of current, you can take as a probe an ordinary targeting lamp, which has a sharp needle at the end of the wire, with which you can pierce the wire. In this simple way, you can check the voltage. Motors with reverse rotation, such as window motors, have two positive connection terminals.
Attention: Check the wiper motor, see the appropriate section.
If there is no voltage at the motor terminals, the cause lies in the power supply. Find the defect using the electrical circuit and eliminate it. Due to the high current consumption, the motors are often switched on via intermediate relays. Check the relay, see the appropriate section.
If no defect is found, check the switch.
If the wire is defective, it is wiser to lay a new wire, since finding the exact location of the wire defect is difficult.