Checking the generator on the car (Mercedes-Benz S-Class W116)

When the car is driven under normal conditions, the charge indicator lamp does not light. If the indicator lamp lights while driving, you need to check the generator or voltage regulator. First of all, check all the wire connections on the generator.

Check the tension of the alternator drive V-belt. If you have a voltmeter and ammeter, you can perform the following checks:

Find the wires on the back of the battery. The red wire is connected to the "B+" terminal of the generator, the small blue wire to the "D+" terminal. For the first check, connect a voltmeter to the "D+" terminal and to ground (do not disconnect the wire and do not turn on the ignition). Voltmeter reading "0".

Turn on the ignition and check that the voltmeter readings correspond to 1...3 V. Otherwise, the cause is a faulty voltage regulator or generator winding.

Start the engine and increase the engine speed to 2000 rpm. Connect the voltmeter to the voltage regulator. The voltmeter readings should be within 13.7...14.5 V. If the readings deviate, the cause may be a faulty voltage regulator or worn generator brushes. At high voltage (about 20 V) the diodes may have burned out.

Connect the ammeter to the "B+" terminal and ground and start the engine. Increase the engine shaft speed to 1200 rpm and turn on the current consumers. The ammeter readings should correspond to at least 30 A. The deviation in readings may be due to damage to the diodes. Other checks can only be performed after removing the generator.

[Article text obtained from the website: MERCEDESMAN.ru]