Charging system (Mercedes-Benz E-Class W124)

If the battery charge indicator lamp does not light when the ignition is turned on, check the wiring to the generator and the integrity of the indicator lamp. If the lamp still does not light, check the electrical circuit from the generator to the lamp. If all electrical circuits are in good order, then the generator is faulty and should be replaced or repaired.

If the battery charge indicator light comes on while the engine is running, stop the engine and check the condition and tension of the alternator drive belt, as well as the connection of the wires to the alternator.

The voltage regulator can be tested as follows.

Connect a voltmeter to the battery terminals and start the engine.

Increase engine speed until the voltmeter readings stabilize, which should show from 12 to 13 volts, but not more than 14 volts.

Turn on the maximum number of electrical consumers (headlights, rear window defroster, heater fan). In this case, the voltage generated by the generator with a voltage regulator should be within the range of 13 to 14 volts.

If the voltage does not correspond to the required values, the cause of the malfunction may be worn generator brushes, weak brush springs, a faulty voltage regulator, a faulty diode, a broken stator winding or defective rotor slip rings.