Steps to Checking the Voltage on an Alternator

Checking a car alternator is easy to do. You will need a voltage meter, but that is the only specialty tool required. The whole process should take no more than ten minutes and you will have either located the problem or eliminated one component of your vehicle's charging system.

An alternator is an essential component of your vehicle. If the alternator is not working properly, your battery will drain and your car will no longer run. If you suspect your alternator is the cause of your car's problems, check the voltage. This voltage is necessary to charge your car's battery and supply power to the vehicle's electrical system.

First you will need to start the car. Run the car at a normal idle. Bring out your voltmeter and connect it across the battery terminals. This will need to be a direct connection. Turn on your headlights and set them to the high beam setting. Now you will need to check the battery voltage. The voltage should range between 13.8 and 14.2 volts. It may go as high as 14.5 volts so don't be alarmed if this is the number you see.

When the above number is in the normal range, you will need to increase the engine speed to approximately 1500 RPM. Check the battery voltage again. It should now read in the range of 14.2 and 14.6. If your display reads less than 14.2, chances are the alternator has a bad diode or two. If this reading normal, you will need to continue testing.

Keep the engine running at 1500 RPM. Turn off the headlights while continuing to run the test. Do so for at least one full minute. The voltage should never go over 14.8 volts. If it does, most likely the voltage regulator is at fault and your battery is being overcharged.

This is all that is required to test the voltage of your alternator. If the problem lies here, you will need to replace this piece. If not, continue checking the car charging system or seek help from a mechanic. The last thing you want is to be stranded on the side of the road.