- a) Check the condition and tension of the alternator drive belt, replace it if necessary (see Chapter Engine);
- b) Check the generator mounting bolts for tightness;
- c) Check the condition of the generator wiring and its terminal connections, remove oxidation products if necessary, tighten the fasteners;
- d) Check the condition of the relevant fuses located in the main assembly block (see Chapter On-board electrical equipment), - before replacing a blown fuse, eliminate the cause of the overload;
- e) Start the engine and make sure that the generator does not make any extraneous noises - a whistle or squeal may indicate wear of the bearings or brushes;
- f) Check the battery charge level - remember that damage to one of the cells may lead to an increase in current consumption;
- g) Disconnect both wires from the battery (negative at first) and carefully examine the condition of the terminals - if traces of corrosion are found, carefully clean the terminals, preferably using special devices, and ensure that the wire tips are securely fixed to the terminals.
2. Check the output voltage of the battery with the engine off - the measurement result should be about 12 V.
3. Without disconnecting the fan from the battery, start the engine and begin to increase its speed until the instrument readings stabilize (about 3000 rpm). The measurement result should not go beyond the range of 13.5÷14.6 V, - the generator must provide recharging of the battery while driving.
4. Turn on as many electrical consumers as possible (outdoor lighting devices, heater fan, rear window heating, etc.) and make sure that the voltmeter readings remain within the range of 13÷14 V - the voltage may drop temporarily, but should return to normal again (you may have to increase the engine speed slightly).
5. If the output voltage exceeds the upper limit of the permissible range, it is necessary to replace the voltage regulator.
6. The cause of excessive undervoltage may be wear of the generator brushes, weakening of the brush springs, regulator failure, diode failure, winding breakage, and damage to the collector rings. The condition of the brushes and collector rings can be checked visually - if there is no obvious damage, the generator should be removed from the car for a more detailed inspection and repair/replacement.
Article was borrowed from the website: mercedesman.ru