Generator repair

The installed generator is not repaired; in case of failure, it is replaced with an interchangeable generator, which is under warranty, as if it were new. However, in most cases, it is possible to have a defective alternator checked by a Bosch Service Center before installing a new alternator. In this case, it may turn out that the generator can be repaired if the malfunctions are minor.

If you suspect a malfunction in the alternator, take the following measurements before removal:

1) check the charging current wire:

- Disconnect the negative wire from the battery and disconnect the connector from the back of the generator or unscrew the wire;

- reconnect the wire to the battery and turn on the ignition;

- Connect a voltmeter to «mass» and any terminal of the multi-pin plug connector, when connected to all terminals, the voltmeter should show a value approximately equal to the battery voltage, otherwise the generator or voltage regulator is faulty;



Pic. 286. Checking the return of current by the generator

2) current output (to check the adjusting resistor of 30 A, in addition to the ammeter, you must also have a voltmeter, they are necessary to create the electrical circuit shown in fig. 286):


- turn on the headlights and the heater electric motor;

- set the motor speed to 3000 min-1 and change the resistance to increase the current consumption;

- the rated current of the three-phase current generator must be reached (70A), and at the same time the voltage should not fall below 13 V;

- turn off the ignition and consumers and disconnect the measuring devices;

3) voltage drop test «positive» parts of the charging current circuit:



Pic. 287. Checking the voltage drop in «positive» parts of the charging current circuit

- create an electrical circuit as shown in fig. 287;

- turn on the headlights, start the engine and measure the voltage drop;

- bring the engine speed up to 3000 min-1 and read the voltmeter reading. If the measured voltage exceeds 0.5 V, then in «positive» parts of the generator high resistance, which should be eliminated;

- turn off the ignition and headlights;

4) voltage drop test «negative» parts of the charging current circuit:



Pic. 288. Checking the voltage drop in «negative» parts of the charging current circuit


- create an electrical circuit as shown in fig. 288, start the engine, turn on the headlights and measure the voltage drop;

- bring the engine speed up to 3000 min-1 and read the voltmeter reading. If the measured voltage exceeds 0.25 V, then in «negative» parts of the generator high resistance, which should be eliminated;

- switch off ignition and headlights, disconnect control wires and the voltmeter;

5) checking the regulator based on the regulation voltage:



Pic. 289. Checking the regulator based on the regulation voltage

- connect the voltmeter and ammeter according to fig. 289;

- start the engine and measure the regulation voltage;

- bring the engine speed up to 3000 min-1 and watch the ammeter. As soon as the value shown by the ammeter drops to a value within 3-5 V, take a reading on the voltmeter, the voltage shown should be in the range of 13.7-14.6 V. If the value on the voltmeter is outside the specified interval, the voltage regulator is faulty.