Checking voltage
1. Connect the voltmeter to the place where the thick wire with red insulation is attached to the generator and to the "ground" (-).
2. Start the engine and bring its speed to medium values. If the voltage regulator is normal, the voltmeter should show a voltage of 13.3-14.6 V. Otherwise, check the carbon contact brushes or replace the voltage regulator. It is possible that the generator itself is faulty if the brushes and regulator are normal. To check the carbon contact brushes, disconnect the ground (-) wire terminal from the battery.
3. Bosch Generators: Remove the rear generator cover if present (see illustration).
4. Remove the two screws securing the voltage regulator (see illustration).
5. Remove the voltage regulator together with the brushes.
6. Measure the distance the carbon brushes protrude from the regulator housing. The length of new carbon brushes is 13 mm. The remaining length of the brushes is 5 mm (see illustrations).
On the right picture is the voltage regulator of old Bosch generators, a = brush length. It should not be less than 5 mm
7. Valeo generators. Remove both screws securing the voltage regulator on the back of the generator.
8. Remove the regulator.
9. Measure the carbon contact brushes. The permissible residual length of the brushes is 5 mm.
Attention! Carbon brushes for Valeo generators are not supplied separately. They must be purchased together with a new voltage regulator. The same applies to the new generation Bosch generators.
Voltage Regulator Carbon Brushes - Replacement
10. Remove the voltage regulator as described above.
11. Unsolder the braided connecting wires and remove the carbon brushes.
12. Remove the pressure springs from the old brushes and secure them to the new brushes.
13. Solder the braided connecting wires.
Caution! Soldering must be done quickly and do not allow tin to get on the connecting wires. Otherwise, they become hard.
Note! When replacing carbon brushes, you can check the condition of the copper contact rings of the generator anchor, on which the brushes slide. If the rings are significantly worn, the anchor can be given to a workshop for grinding.
Removal
14. Disconnect the negative (-) battery terminal.
15. Four-cylinder engine. Remove the protective cap from the generator mounting bolt, if present.
16. Five-cylinder engine and diesel engines. Remove the engine splash guard.
17. Four- and five-cylinder engines and diesel engines. Disconnect the power cable and the ground (-) cable, if equipped.
18. Loosen the alternator belt tension bolt on the tension bracket.
19. Remove the V-belt or ribbed belt.
20. Remove the generator mounting bolt. While doing this, hold the generator so that it does not fall.
21. Six-cylinder engine. Remove the engine splash guard.
22. Remove the V-belt.
23. Disconnect the power cable and air cooling hose from below.
24. Unscrew the mounting bolts and remove the generator.
Recommendations: If the generator or voltage regulator fails, the trip can be continued. Charging the battery during daytime driving is enough for about five hours of travel. Power is needed for the ignition and fuel injection control unit, as well as the electric fuel pump. In winter, the situation is complicated by the fact that it gets dark early and you have to turn on the low beam headlights.
If possible, do not turn off the engine, so as not to waste battery power on the starter. Turn off the rear window heating, the interior blower and the radio. Do not turn on the windshield wipers unless necessary. At night, drive without switching to high beam headlights. It is recommended to disconnect and insulate the generator wire, so that a faulty generator does not contribute to the discharge of the battery.
For diesel vehicles, the fuel shut-off valve must be turned off (tD engines), see the relevant chapter.
The electronic power supply system of the TDI engine requires a constant supply of electricity. However, the battery charge is sufficient for about five hours of operation.