Guide to Testing Your Alternator

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Guide to Testing Your Alternator

A vital component of a vehicle's operation, the alternator not only enables the battery to stay charged, but it also creates electrical current to power accessories within the car, such as the headlights and radio. Hence, it's crucial that drivers pay attention to how the alternator is doing. Signs that the alternator has issues can be obvious, like a battery warning light on the dashboard, dim lights or the engine cranking slowly. Other indications include problems with the alternator belt, a growling or squeaking noise from the engine, the smell of burnt rubber and loose or disconnected wires. If such a situation arises, it's time to test the alternator.


How to Test the Alternator

The alternator is situated at the front of the engine on the right side and has wires attached to it. Testing how the alternator is running is rather straightforward.. If everything appears normal with the standard voltage test, then drivers can try other troubleshooting tactics to see where the problem exists. To begin, follow this process to inspect the alternator. Note that having a helper makes each step easier.

Gather All Necessary Equipment

Basically, all that's needed is a multimeter or a voltmeter for reading the voltage and a pair of gloves for protection. All of this equipment can be found at auto shops and at e-commerce stores. When testing and the engine is running, do not break or make any connections with the voltmeter, as doing so can cause damage to the car's electrical devices.

Test the Battery

Ensure the battery is working fine prior to testing the alternator, as the battery gets the alternator running, and the alternator then restores energy to the battery. Make sure the engine is off. Open the hood and find the battery. Grab the voltmeter. Link the positive red probe with the positive red terminal, and link the negative black probe with the negative black terminal. If the voltage exceeds 12.2, it is fine. If it doesn't reach that level, charge the car battery with a charger before continuing.

Test the Alternator with Engine Off

Locate the alternator. Grab the voltmeter, turn it on and set it to 20 volts. Connect the red probe to the alternator's positive terminal connector (also red), and connect the black probe to the alternator's negative terminal connector (also black). Be aware that the terminals must be clean to get an accurate reading. The voltmeter should read roughly 12.6 volts.

Test the Alternator with Engine On

Turn on the engine and the check the voltmeter. The desired voltage is somewhere between 13.8 and 14.7 volts -- a sufficient amount to charge a 12.6-volt battery. If it's significantly higher (15.7 volts, for instance), the alternator is most likely overcharging the battery and is faulty, which can cause damage to the battery. If it's right in the middle of that rang (14.2, for instance), everything is fine (so far). If it's significantly lower (12.8, for instance), the alternator is most likely not adequately charging the battery and is probably incapable of powering accessories and the battery simultaneously. However, the read could not reflect how the alternator is functioning, as the engine hasn't been revved up; this is what makes the next step important.

Test the Alternator with Engine at 2000 RPM or Greater

Gas the engine up to 2000 revolutions per minute (RPM). If the voltage still reads low, see if the alternator belt is spinning tightly and smoothly. If nothing is wrong with the alternator belt, then the alternator isn't functioning as it should.

Test the Alternator by Straining It

Turn on the radio, every light possible, the air-conditioning and more to put a heavy load on the alternator. With all those accessories on and the engine running, the voltage should still be above 13, and hopefully no lower than 12.7. If it goes lower, a problem exists with the alternator. Remember to turn off the engine prior to disconnecting the voltmeter


If the Alternator Fails the Test

If the alternator doesn't read as it should, it may have to be replaced. Alternators can be found at automotive stores throughout Australia as well as online. Prior to getting a replacement, consider trying these troubleshooting tactics first. It may be a less significant problem or simply an issue with the reading.

Check the Wires and Alternator Belt

Make certain the wires coming in and out of the alternator are securely connected. Look specifically for damage, such as fraying or corrosion. Make sure the alternator circuit connects cleanly all the way to the battery. Additionally, ensure the alternator belt is spinning nicely.

Sand the Alternator Terminals

Perhaps the alternator terminals aren't clean, which can interfere with the alternator charging the battery. Sand the terminals with sandpaper and test again. If the voltage readings remain the same, then the alternator isn't in proper condition.

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