The first step is always to check the fuse if the electrical circuit is protected. The location of the fuses is given in the table on the fuse box cover, see also Section Replacing fuses.
If necessary, replace the faulty fuse, and after switching on the power consumer, check whether the fuse has blown again. In this case, you must first find and fix the fault, as a rule, we are talking about a short circuit. This means that in some place, maybe also inside the device, the ground and plus are connected to each other. Second step: If the lamp does not light or does not work with a good fuse, you should check the voltage supply.
Checking the lamps
1. Remove and inspect the lamp. If the filament has burned out or the glass bulb has become loose in the base, replace the lamp.
2. To determine if the lamp is working properly, proceed as follows: Connect one positive wire and one ground wire directly to the battery terminals and connect them to the lamp. It does not matter how the wires are connected to the lamp. If the lamp does not light, replace the lamp.
Note: Make sure that the contacts on the lamp and in the socket are not corroded. If necessary, clean the contacts with sandpaper.
3. If the lamp is OK, insert the lamp and turn it on. If the lamp does not light, check the voltage supply with an indicator. To do this, attach the voltage indicator to the ground. This means: One cable of the indicator must be connected to a reliable ground point on the engine (bare metal) or directly connected to the battery ground pole. Connect the other positive probe of the indicator either to the plug or to the cable. If the indicator lights up, but the lamp still does not light, the ground supply to the lamp is interrupted. To check, connect the auxiliary ground wire to the ground of the lamp socket. The lamp should light up.
Note: There are lamps that only have a conductive wire, such as parking lights, interior lighting. These lamps are connected through their housing directly to the vehicle's ground.
4. If there is no voltage on the lamp's current-carrying cable, i.e. the indicator does not light, it is very likely that the switch is faulty. Check the switch for current flow.
Checking electric motors
1. More and more comfort functions in the car are performed by small electric motors. This applies, for example, to the window lifts, the sunroof, the electric central locking device or the electric antenna drive.
2. Each motor is switched on when needed by a switch, in most cases by hand. The electric antenna is controlled automatically by the radio receiver.
3. Check the fuse of the corresponding electric motor and replace if necessary.
Note: For electric windows and central locking, the cause of the overload must be eliminated before re-activation. This may be icing of the windows or locks, or contamination of the glass guides.
4. If the new fuse blows immediately, there is a short circuit.
5. To determine whether the fault is in the motor, connect 2 auxiliary cables to it (diameter 2 mm) directly from the battery. Positive cable to the positive pole, ground cable to the ground pole of the electric motor. If in doubt, determine the location of the poles using the diagram. To do this, the electric motor must be removed. All electric motors in the car are powered by the on-board network (12-14 V). If the motor now works normally, the fault is in the wiring.
Note: If the motor runs too slowly or intermittently, this may indicate that the carbon brushes are worn out. In this case, replace the brushes.
6. If the engine is running, use the diagram to determine which wires supply voltage to it if the switch is on or the ignition is previously turned on.
7. Check the current-carrying wire on the electric motor using an indicator. Since electric motors carry a lot of current, you can use the old indicator with an incandescent lamp. The indicator has sharp probes that can be inserted into the cable. This is the easiest way to check the voltage. Motors that rotate to the right and left, such as window lift motors, have two positive poles.
Caution! For checking the windshield wiper motor, see Chapter Removal and installation the front wiper motor.
8. If no voltage is applied to the motor, the wiring is faulty. Find and fix the fault using the diagram. Electric motors, due to the need for high current, usually have additional switching relays. For checking, see Chapter Removal and installation the front wiper motor.
9. If no fault is found, check the switch.
10. If the cable is faulty, it is more advisable to lay a new one, since it is very difficult to find the place where the cable is broken.