Until about the end of 1991, some AUDI 80 models were equipped with a 65-A generator. They were replaced by 90-A generators. With a special configuration, generators 110 and 120-A can be installed. The generator generates a voltage of 14 V when the on-board network needs 12 V. Due to this difference, the battery is charged.
The drive of the generator with a V-belt or ribbed belt from the crankshaft pulley is designed so that even when the engine is idling, the generator can generate current at ⅔ of the maximum performance (see illustrations 4.0a).
Illustration 4.0b shows a newer model Bosch generator, which differs from the previous ones with a 1.2-terminal B + cover (to the battery).
Due to the fact that the battery can only be charged with direct current, the alternating current generated by the generator is converted into direct current by a suitable diode rectifier. Rectifier diodes are very sensitive to high voltages. For this reason, some precautions must be observed:
- do not disconnect or connect the wires between the battery and the generator while the generator is running. The resulting voltage peaks can damage the diodes.
- The alternator must not run with the battery disconnected.
- all connections from the generator, including wire «masses» (-), must have good contact.
- disconnect the battery when performing welding work on the body.
The crankshaft, from which the generator is driven, rotates, depending on the traffic situation, with a lower or higher number of revolutions. According to the rotation of the crankshaft, the generator generates less or more current, which is unacceptable for consumers of the on-board network. For this reason, the generator is equipped with a voltage regulator that maintains the voltage from the generator within 14 V, regardless of the generator speed.
There is a battery charging indicator light on the instrument panel. It has two positive contacts (+). One of them receives power from the D + terminal of the generator (blue insulated wire), and on the second - from terminal 15 through the multi-pin plug of the ignition switch (wire with black insulation).
When the ignition is switched on, terminal 15 supplies power to the control light. However, the generator has not yet started and therefore the D+ terminal acts as «weight» (-). The control lamp lights up. When the engine is started from the D+ terminal, the generator also starts to receive power and the control lamp goes out. An extinguished battery charging indicator light is not proof that the battery is being recharged. It may happen that the consumers of the on-board network take more from the battery than it receives from the generator. This is possible if the alternator is weak and unable to recharge the battery. The battery charging indicator light will not light up in such cases.
The generator is practically maintenance-free, except for the rare replacement of carbon contact brushes. Repairing a damaged generator at home is not possible.
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