1. Start the engine and let it run for at least 15 minutes. Remove the protective cover from the generator terminal "30" and, having set the engine speed to 3000–3500 min⁻¹, measure the voltage at the terminal "30". To do this, connect one terminal of the voltmeter to the generator terminal "30" and the other to the generator body. The voltmeter should show a voltage of 13.6–14.6 V.
Checking the generator rectifier block
You will need a test lamp (12V, 3W).
Attention! A burning lamp when checking negative diodes may also indicate a short circuit of the stator winding to the generator housing, however, such a malfunction occurs much less frequently than a short circuit of the diodes.
2. Check the rectifier block diodes with a 12V test lamp and battery (see explanation). To check for a short circuit in the positive and negative diodes, connect the "+" of the battery via a test lamp to the "30" terminal of the generator, and the "-" of the battery to the generator body. If the lamp lights up, there is a short circuit in the diodes and the unit needs to be replaced.
Explanation. You can check the rectifier unit without removing the generator from the car. To do this, disconnect the wires from the battery and the generator, and remove the connector with the wire from the voltage regulator terminal. For clarity, the check is shown on the generator removed from the car.
3. To check the positive diodes, connect the "+" of the battery via a test lamp to the "30" terminal of the generator, and the "-" of the battery to one of the rectifier unit mounting bolts. If the lamp lights up, there is a short circuit in the positive diodes and the unit must be replaced.
4. To check the negative diodes, connect the "+" of the battery via a test lamp to one of the rectifier unit mounting bolts, and the "-" of the battery to the generator housing. If the lamp lights up, there is a short circuit in the negative diodes. The unit must be replaced (see warning).
5. To check the additional diodes, connect the "+" of the battery via a test lamp to the "61" terminal of the generator, and the "-" of the battery to one of the rectifier unit mounting bolts. If the lamp lights up, there is a short circuit in the additional diodes. The rectifier unit must be replaced.