While your engine is running, your car's alternator charges your battery so that it can power all of your car's electronics, including the spark you need to start it. If your alternator isn't working properly, you could find yourself stuck in the middle of nowhere. Here's how to test the power of your car's alternator, so that doesn't happen to you.
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| How to test alternator |
To test your alternator, you'll need a voltmeter and an ammeter, or a multimeter that reads both voltage and amperage.
1) Check the battery: Before you can tell if your alternator is working properly, you need to see what's going on with your car battery. With the engine off, connect the positive side of your voltmeter or multimeter to the positive terminal of your battery and the negative side to the negative terminal. The reading should be about 12.7 volts. If it's below 12.4 volts, the battery may need to be replaced.
2) Check the alternator voltage: Turn on your engine, but do not press the gas. When the engine is on, the alternator is supposed to send electricity to the battery. Check your voltmeter or multimeter again and read the voltage. If your alternator is working, the voltmeter should read between 13.8 and 14.2 volts.
3) Check the alternator amperage: Disconnect the voltmeter and connect an ammeter (if you are not using a multimeter) to your battery the same way you connected the voltmeter. Turn on all of the car's electrical equipment: lights, stereo, windshield wipers and anything else you can. Let the engine idle at about 1200 rpm. Check your car's manual or parts manual to see what your maximum alternator amperage should be. The amp reading on your meter should be close to the maximum output. A 90 amp alternator will produce about 88 amps. If your amperage is too low, you probably need a new alternator.
Read also: EVERYTHING YOU NEED TO KNOW ABOUT TORQUE CONVERTERS
How to test alternator