When the engine is running, the main source of current - the generator - supplies electric current to all consumers, including the ignition system, and charges the battery.
If the red low battery indicator light is on in the instrument cluster, it means that the current is not flowing from the generator to the on-board network and the battery's energy reserve is being used up. It is unacceptable to operate the car with the low battery indicator light on, since sometimes the cause of the light may be a short circuit in the wiring, leading to a fire in the engine compartment of the car. Stop the car, turn off the engine and determine what malfunction caused the light to come on. If the cause of the malfunction was not a short circuit, and the battery was fully charged, you can drive to the garage without the generator, but it is better to try to fix the malfunction on the spot.
Checking electrical equipment
1. Check whether the accessory drive belt is broken. If it is broken, replace the belt (see "Replacement of auxiliary drive belt").
2. If the belt is intact, check its tension (see "Checking the accessory drive belt").
3. After checking the belt, check the wires connected to the positive terminal of the battery...
4. ...to the starter.
5. ...and to the generator. The wires may be torn, broken inside the insulation, or have oxidized or unreliable contacts. Fix the problem and start the engine. If charging current appears, you can continue driving.
6. If the belt tension is correct, check fuse No.69 (see "Location of fuses, fuse links, relays and their replacement") in the fuse and relay box located in the engine compartment. If the fuse is blown, replace it, start the engine and check if the battery discharge lamp goes out. If the lamp goes out, you can continue driving.
Warning: Do not install a fuse with a higher rated current, as this may cause damage to the electrical equipment or even a fire.
If after the measures taken the discharge lamp continues to light with the engine running, then the possible cause of the malfunction lies in the generator itself. There may be several reasons, and it is better to eliminate them in a car service or garage, and you can only hope that the battery power reserve is enough to get to them.
Helpful Hint: To reduce current consumption when driving a vehicle with a faulty alternator, if possible, turn off the audio system, unnecessary lighting devices, heater fan, rear window heating, etc.