The unpleasant consequences of a generator failure are obvious: the battery stops charging, on which the entire onboard load falls. But this is half the trouble: the increased voltage threatens the failure of all the electronics of the car. However, you should not rush to buy a new device - in some cases, it is enough to replace some of its elements, which will cost much less.
The design of the VAZ2115 generator includes, in addition to the rotor, stator, a relay regulator with valves (diode bridge). To determine which element is "to blame" for the generator failure (or its poor performance), you can first check the auto, without removing the generator.
Relay-regulator
You will need an assistant to test the regulator. Ask him to start the engine and bring the number of revolutions to 3000. In this case, it is necessary to turn on the dimensions with the high beam, the "stove", the rear window heater. Use a tester to measure the voltage on the battery, which must exceed 13.2V (generator 9402.3701), or 13.6V (generator 37.3701). If the voltage is much lower than this value, it means that the generator windings (short circuit, open circuit), the relay-regulator are “to blame”, or there is no contact on the rings of the excitation winding (due to oxidation). Indirectly, it is possible to determine the malfunction of the relay-regulator when the main beam is on (other consumers must be turned off). To do this, measure the voltage again, which should correspond to the same 13, 2 or 13, 6V.
It is more reliable to determine the operability of the regulator on the removed generator, relay-regulator. Take a 12V test lamp and connect it between the brushes. At the same time, apply a constant voltage of 12V from a suitable power supply, connecting the plus to the “D +” terminal, and the minus to the car ground. The lamp should light up. With a smooth increase in voltage to 16V, it will go out. If this does not happen, in any case the regulator will have to be changed. If you have a 37.3701 generator, then the plus of the constant voltage source should be connected to the contacts "B" and "C", and the minus to the ground.
Generator valves (rectifier unit)
For monitoring, a battery and a warning lamp are enough. Connect the plus of the battery through the control lamp to the contact "B +" on the generator (if 37.3701, then to the contact "30"), minus - to the body. A lit lamp indicates a breakdown or short circuit in the valve block (both negative and positive). To make sure that the block of positive valves is in good working order, connect the battery plus to the same contact ("B" or "30"), minus with any phase winding through the test lamp. A lit light bulb indicates a breakdown of one of the valves.
You can check the negative valves (diodes) if you connect any phase winding to the ground (generator case) through the lamp. Burning the lamp indicates a short circuit of the stator windings with the generator case or a breakdown of one of the valves. Each of them can be checked with a tester (ohmmeter), but you will have to disconnect one of the diode contacts. It is better to change the rectifier unit assembled; it is recommended to do this in a specialized workshop.
