The first step is always to check the fuse, as it protects an electrical component of the structure. The actual location of the fuses can be seen on the printout located on the fuse box cover, see also p. "Replacing fuses".
If necessary, replace the faulty fuse and after connecting the electrical consumer, check whether it has blown again. In this case, first of all, it is necessary to detect the fault and eliminate it, here, as a rule, we are talking about a short circuit.
Second check step: If the incandescent lamp does not light up with a working fuse, or, accordingly, the electric motor does not work, then the power supply system should be checked.
Checking an incandescent lamp
Remove and inspect the bulb. If the filament is burnt out or the glass bulb sits loosely in the base, the bulb should be replaced.
To determine if an incandescent lamp is working properly, proceed as follows:
Connect the positive wire (+) and the ground wire (-) directly to the battery terminals and connect them to the lamp. It does not matter which wires are connected to the lamp. Connect one wire to the current lead, the other to the incandescent lamp housing. If the lamp still does not light, replace it.
Note! Make sure that the contacts on the lamp and lamp socket are not corroded. If necessary, sand down corroded or bent terminals with sandpaper and make a normal contact.
If the bulb is OK, insert it and turn it on. If the bulb does not light, check the power supply using a test lamp. To do this, connect the test lamp to the car's ground. That is, one wire of the test lamp should be connected to a good point on the engine housing (polished metal) or directly to the negative pole of the battery. Keep the other probe of the test lamp (+) either on the current-carrying plug or connect it to a wire that is under voltage. If now the test lamp lights up, but the bulb still does not light, then the line connecting the car body to the incandescent bulb is broken. To check this, attach an auxiliary wire connected to the car body to the lamp socket. Now the incandescent bulb should light up.
Note! There are lamps that are equipped with only one live supply line, such as parking lights, interior lights of a car. These lamps are directly connected to the vehicle mass via their housing.
If there is no voltage in the current-carrying wire to the lamp and the control lamp does not light, then it is very likely that the switch is faulty. Check the switch for current flow.
Checking Electric Motors
In a car, ever-increasing comfort is provided by low-power electric motors. These include, for example, the window lift, the sliding roof panel, the centrally controlled door locking system or the electric antenna. If necessary, each electric motor is switched on by means of a single switch, usually manually. In the case of the electric antenna, the switch is automatically controlled via the radio.
Check the resistance of the corresponding electric motor, replace it if necessary.
Note! Before reactivating, eliminate the cause of the overload of the electric window lift and central locking system. This could be, for example, frozen windows and locks or dirty window channel grooves.
If the fuse immediately blows again, this indicates a short circuit.
To determine for sure whether there is a fault in the engine, run two auxiliary wires with a diameter of about 2 mm directly from the car battery to the electric motor. Connect the positive wire to the positive pole, and the wire connected to the housing to the ground pole. In case of doubt, the distribution of the poles is determined from the basic diagram of the electrical equipment. If necessary, you need to disassemble the electric motor for this. All electric motors in the car are powered by on-board voltage (from 12 to 14 volts). If the electric motor now works normally, the power supply system was faulty.
Note! An electric motor that rotates too slowly or runs intermittently may indicate that the sliding electrographite contacts are worn out. In this case, replace these contacts.
If the engine is running, use the electrical diagram to determine which supply wire supplies voltage to the electric motor when the switch is activated with the ignition previously on.
Use a test light to check the live wire in the electric motor. Since electric motors carry a lot of current, you can replace the regular test light with an incandescent light bulb. These lights have pointed test needles that you can use to puncture the connecting wire. This is a simple way to check the voltage. Motors that alternately rotate left/right, such as window lift motors, have two positive terminals.
Caution! Check the windscreen wiper motor, see the relevant section.
If there is no voltage supplied to the electric motor, then the power supply system is faulty; find the defect in the supply line according to the electrical equipment circuit diagram and eliminate it. As a rule, due to high current consumption, electric motors have an additional switching relay, see the corresponding section.
If no fault is found, check the switch.
If a wire is damaged, it is often more rational to lay a new wire, since it is difficult to determine the location of the break under the insulation.