Testing the alternator or battery in your car requires a digital multi-meter with a voltage setting on it. The battery in your car has a rating of 12 volts and should have at least that to start your car. If the voltage is low on the battery, the alternator needs to be checked to rule out a problem with the charging system before you replace the battery. You can test the system with a multi-meter to determine the output of the battery and the alternator, giving you a better idea of the condition of your battery and alternator.

Step 1

Turn the dial on your multi-meter to the 20V setting. This will allow you to read the voltage from your battery and alternator.

Step 2

Place the red test lead from the multi-meter on the positive post of the battery. Place the black test lead on the negative battery post. Note the reading on the meter, …