Richpin demonstrates how to test an alternator with a standard multimeter. First make sure that the vehicle's battery is fully charged. Take the negative lead of the multimeter and put it on the negative post of the battery. Place the positive lead of the meter on the positive lead of the battery. Set the meter to DC voltage using the 20 scale and read the display to ensure the battery is fully charged. Next start up the vehicle and see what the alternator is producing. The display should now read one volt over the initial reading. If the reading remains the same, then the alternator is not producing any electricity. Now, turn on the lights and heater blower to see, if the alternator is weak. Let the car run for a while and if the display holds its reading, then the alternator is working fine.