See part numbers for this unit. Here.
Alternator replacement described Here.
Bosch generator: 1 - generator pulley; 2 - front cover; 3 - stator; 4 - coupling bolt; 5 - back cover; 6 – brush holder with voltage regulator; 7 – brush holder connector; 8 - output «B+»; 9 - casing
«Minus» battery must always be connected to «mass» car, and «plus» - to the conclusion «B+» generator. Reverse connection will lead to a breakdown of the generator rectifier unit diodes.
Brush assembly with voltage regulator (brush holder) is under the cover (casing) generator. The voltage regulator is a non-separable unit; in case of failure, it is replaced as an assembly with a brush holder. To replace it you need remove generator, remove the casing from the generator and unscrew the 4 screws of the brush assembly.
Brush holder with voltage regulator: 1 - contact «masses»; 2 – brush holder body; 3 - voltage regulator; 4 - electrical connector; 5 - contact «B+»; 6 - brushes
Generator malfunctions
The principle of operation of the alternator
Alternator rotor (sometimes called an alternator) driven by the engine through a belt drive. Due to electromagnetic induction, the magnetic field of the rotor excites the current in the stator windings (pic. 4.20 and 4.21).
Pic. 4.20. The lines of force of a rotating magnetic field penetrating a closed conducting circuit excite an electric current in it
Pic. 4.21. The device of a typical alternator (alternator)
Measurement of the battery charging voltage is carried out according to the following method
1. A voltmeter is connected to the battery, observing the polarity.
2. Set the voltmeter to DC voltage measurement mode.
3. Start the engine and bring the speed of its rotation to increased idle speed (about 2000 rpm).
4. Record the voltmeter reading and compare it with the passport value (pic. 4.22). If the measured voltage is lower than the nameplate, before replacing the generator, charge the battery and check the voltage in the charging circuit again.
Pic. 4.22. The digital multimeter must be set to DC voltage measurement mode and connect its red wire to the positive terminal, and the black wire to the negative terminal of the battery
Advice
If the voltmeter reading first rises and then falls as the engine speed increases, the alternator drive belt is loose or slipping.
Check that the fuse is working with a test light.
Most generators have a plug-in connector with a fuse in the cable connecting the terminal on the rear cover of the generator closest to the slip rings of the current collector with the positive battery terminal. If this connection fails (fuse blown) the battery charging system becomes inoperable. More than once it happened that the generator was removed, and then put back in its place, only because this blown fuse was not paid attention to in a timely manner. A quick and easy way to check the health of the fuse is to touch the probe indicator light probe, the second end of which is connected to ground, to the output terminal of the generator. If the light is on, then the fuse is good. This check makes sure that the circuit between the alternator and the battery is not broken.
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Pic. 4.23. A simple and convenient measuring cable can be made from a two-wire cable, a cigarette lighter plug and two banana plugs ("bananas"), which fit into the COM and V jacks of most digital meters (A). By connecting a measuring device to the cigarette lighter socket with this cable, you can easily measure the voltage in the charging circuit of the battery (b).
Use the cigarette lighter socket
Battery voltage can be measured through the cigarette lighter socket (pic. 4.23). To do this, you need to make a cable adapter. Take a two-wire cable and connect to it on one side a cigarette lighter plug, and on the other side two single-pole plugs with longitudinal spring contacts (so called "bananas"). These plugs fit! to the COM socket (general) and the voltage test socket of most measuring instruments.
Alternating voltage control at the generator output
There should be no AC voltage at the output of a working alternator. Rectifier diodes installed in the alternator must rectify the alternating voltage generated by the alternator, converting it to direct voltage. AC voltage control is performed according to the following method:
Step 1. The digital meter is set to measure AC voltage.
Step 2. Start the engine and bring its speed to 2000 rpm.
Step 3. Connect a voltmeter to the battery terminals.
Step 4. Turn on the headlights to load the generator.
Note
To obtain more accurate readings, a voltmeter is connected to the output terminals of the generator.
The measurement results are interpreted as follows: if the rectifier diodes are good, the amplitude of the AC voltage measured by the voltmeter should be less than 0.4 V. If it exceeds 0.5 V, this means that the rectifier diodes are faulty.
This technique is not suitable for diagnosing faulty diodes.
Checking the power generated by the generator
The power supply system may be able to provide the required voltage, but at the same time unable to provide the required power. If there is any doubt about the power generated by the power supply system, first of all it is necessary to check the tension of the alternator drive belt. With the engine off, try turning the generator fan by hand. If this succeeds, replace or adjust the tension of the drive belt. On fig. Figures 4.24 and 4.25 show how the test equipment is connected to check the output power of the generator.
Checking the output power of the generator is carried out according to the following procedure:
Step 1. Connect the test equipment cables to measure the power of the generator in starting and charging mode in accordance with the manufacturer's instructions.
Step 2: Turn the ignition key (engine not running) and record the ammeter reading. This measurement gives the amount of current consumed by the ignition system - it should be between 2 A and 8 A.
Pic. 4.24. Typical test equipment connection diagram for current measurement in starting and charging mode
Pic. 4.25. The pliers of the current measuring inductive sensor must cover all cables coming from the battery terminal. What kind of cables these will be - positive or negative, it does not matter, because an equal current flows from the battery and flows into it
Step 3: Start the engine and bring the speed to 2000 rpm (increased idle speed). Slowly turn the load adjuster until you get the maximum ammeter reading. Record this reading.
Step 4. Add the ammeter readings obtained in step 2 and step 3. The result should not differ by more than 10% (or 15 A) from the rated output current of the generator.
If the measured current differs from the rated output current of the generator by more than 10%, repeat the test by turning off the voltage regulator and applying full field current through the generator rotor field winding.
Pic. 4.26. The rated output current of most GM alternators is stamped on the front cover, either on the side of the front cover facing the alternator drive pulley or on top, under a small boss with a threaded mounting hole
Note
When adjusting the amount of load applied to the battery when testing the generator for output current using test equipment equipped with a carbon rheostat, be careful not to allow the battery voltage to drop below 12 V. The maximum output current for most generators is achieved at a voltage above 13 IN.