Voltage test
1. Connect a voltmeter to the place where the thick wire with red insulation is attached to the generator and to «mass» (-).
2. Start the engine and bring its turns to average values. If the voltage regulator is normal, then 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 the regulator are normal. To check the contact carbon brushes, disconnect the wire terminal «masses» (-) from the battery.
3. Bosch generators. Remove if there is a back cover of the generator (see illustration).
4. Remove the two screws securing the voltage regulator (see illustration).
5. Remove the voltage regulator along with the brushes.
6. Measure the distance the carbon brushes protrude from the regulator housing. The length of the new carbon brushes is 13 mm. Residual length of brushes 5 mm (see illustrations).
In the right illustration, the voltage regulator of generators of old Bosch models, 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 alternator.
8. Remove the regulator.
9. Measure the carbon contact brushes. Permissible residual length of brushes 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 new generation Bosch generators.
Voltage regulator carbon brushes - replacement
10. Remove the voltage regulator as above.
11. Unsolder the braided connecting wires and remove the carbon brushes.
12. Remove the pressure springs from the old brushes and attach them to the new brushes.
13. Solder the braided connecting wires.
Attention! Soldering should be done quickly and avoid getting tin on the connecting wires. Otherwise, they become rigid.
Note! When replacing carbon brushes, you can check the condition of the copper slip rings of the generator armature, on which the brushes slide. If the rings are significantly worn out, then the anchor can be given to the workshop for grinding.
Withdrawal
14. Disconnect the wire terminal «masses» (-) from the battery.
15. Four-cylinder engine. Remove, if there is a protective cap from the alternator mounting bolt.
16. Five-cylinder engine and diesel engines. Remove the engine mudguard.
17. Four- and five-cylinder engines and diesel engines. Disconnect the power cord and wire «masses» (-), if any.
18. Turn out a bolt of a tension of a belt of the generator on a tension bracket.
19. Remove the V-belt or ribbed belt.
20. Turn out a bolt of fastening of the generator. While doing this, hold the generator so that it does not fall.
21. Six-cylinder engine. Remove the engine mudguard.
22. Remove the ribbed belt.
23. Disconnect, working from below, the power cable and air cooling hose.
24. Turn out bolts of fastening and remove the generator.
Recommendations: If the generator or voltage regulator fails, the trip can be continued. Charging the battery when driving during the day is enough for about five hours of travel. Power is needed by 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 dipped headlights.
If possible, do not turn off the engine so as not to waste battery charge on the starter. Turn off the heated rear window, the interior blower and the radio. Do not turn on the windshield wiper unnecessarily. At night, drive without switching to high beam headlights. It is recommended to disconnect and insulate the alternator wire so that a faulty alternator does not drain the battery.
For vehicles with a diesel engine, it is necessary to disable the fuel cut-off valve (TD engines), see the relevant chapter.
The electronic power supply system of the TDI engine needs a constant supply of electricity. However, the battery charge lasts approximately five hours of operation.
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