The alternator is an important part of any vehicle. After the battery starts the car, the alternator recharges your battery to keep your car running smoothly. And it helps keep all the other electronics in your vehicle powered while the car is on. This guide will teach you how to test your alternator at home, so you can make sure it is functioning at top capacity.
Five Steps To Test Your Alternator At Home
Eventually, like every part of a car, your alternator will fail. Every car is different. Sometimes your alternator might die at 80,000 miles. Or, if you’re lucky, it could last until more like 150,000 miles. Knowing the warning signs of a failing alternator and regularly checking its condition can help you stay one step ahead of a dying alternator.
How to Test Your Alternator
1. Collect your tools. You will need something to read the voltage/amperage of your battery and alternator. A cheap multimeter or a voltmeter will be able to test your alternator without hurting your engine. Set your multimeter to DC volts.
2. Turn off your engine. You will first need to get a base voltage reading from your battery and will need to do this while the engine is off.
3. Test the battery voltage. Touch the black meter lead to the negative battery terminal and the red meter lead to the positive battery terminal. Make sure that your battery terminals are clean, and you have a clear surface where you can get a solid point of contact for the lead. Your reading should be around 12.6 volts. If the voltage is lower than 12 volts, the issue might be with your battery. If this is the case, you will likely need to charge or replace your battery before you will be able to accurately test your alternator.
4. Turn on your engine and test the voltage again. The meter should read between 14.2 and 14.7 volts without any lights or electronics on. If it is lower than that, you may need to replace your alternator. If it is above that, your alternator may be overcharging your battery.
5. Test the load voltage. If you have an assistant, have them rev the engine to about 2,000 RPM while you monitor the voltage reading. Or if you are on your own, with your car still running, turn on your radio, lights, and any other electronic accessories and check the voltage reading. Though you will likely see a slight drop in the voltage with this added stress on the battery, the voltage reading should not drop below 13.0 volts.
If your voltage readings are outside of these ranges, check to make sure that the battery leads are securely connected to the terminals, that the wires around your alternator are all plugged in and in good condition, and that your alternator belt is tight. If after that, your voltage readings are still outside the standard range, you should consult with a professional mechanic on the next steps.