Not sure if the alternator is working at its best? It's hard to tell if this component of your car is producing the right voltage or not if you don't know what to check. The simplest way to test an alternator is to use a voltmeter. If, on the other hand, you have a certain sensitivity and ear, you may want to try other methods. These tests will be used to check the general conditions of the alternator and battery. Some newer vehicles, however, may have electronically controlled charging systems and will need more in-depth testing.
Steps
Method 1 of 2: Use a Voltmeter
Step 1. Purchase a voltmeter
You can find it in auto parts stores even for less than 30 €. Avoid buying a very expensive one - even cheap ones will be great for performing the following checks.
If you already own a multimeter you can use it directly, avoiding an additional expense. This meter is capable of controlling many other electrical parameters, such as resistance and current, in addition to voltage. In any case, to verify the proper functioning of the alternator, only this last parameter will be important
Step 2. First of all check the battery
This is necessary to start the engine which, subsequently, rotates the alternator at a speed sufficient to recharge the battery. If the charge level is insufficient, you will not be able to start the vehicle and therefore you will not be able to carry out the following tests. If you are in the cold season and your battery is old, the source of your problems may be the latter and not the alternator, and this is why it is necessary to check it before focusing on the other component. Here's how to do it:
- Turn off the engine before connecting the voltmeter.
- Open the hood.
- Connect the voltmeter to the battery. Connect the red lead of the voltmeter to the positive terminal of the battery and the black one to the negative terminal. Avoid touching the battery without protection.
- Read the measurement on the voltmeter. If the value is greater than 12.2 volts, the battery is charged enough to start the engine and you can then proceed further.
- If the battery voltage is too low, recharge it or try a different method to check the alternator.
Step 3. Start the car and run the engine to 2000 RPM
In this way, a lot of power will be drawn from the battery, causing the voltage regulator to put the alternator into play.
Step 4. Keep the engine running and check the battery voltage once more
At this point you should read a value of at least 13 volts; by varying the engine speed the voltage should fluctuate between 13 and 14.5 volts. If, on the other hand, the voltage does not change or even decreases, then the alternator has some problems.
Repeat the procedure by turning on the headlights, the radio and the air conditioning. The alternator is able to recharge the battery if the voltage supplied is greater than 13 volts while the engine is running at 2000 rpm and all the devices are on
Method 2 of 2: Check the alternator
Step 1. Check the voltage indicator
If your car is equipped with it, this tool will check the supplied voltage. Bring the engine to 2000 rpm and turn on the air fan, air conditioner or heating, lights and any other device that consumes electricity, checking if the indicated voltage drops. Generally, if you read a higher value with the engine on than with the engine off, you can assume that the alternator is working correctly.
Step 2. Listen to the alternator while the engine is running
Should there be a failed bearing, a screeching sound should be heard from the engine compartment that increases in intensity as you activate multiple electrical accessories at the same time.
Step 3. Turn on the radio and increase the engine speed
Tune the system to a low frequency in AM, where no music is transmitted. If the radio screeches or you hear electrical noise coming from the speakers every time you accelerate, the culprit will most likely be the alternator.
Step 4. Look for a workshop that will check the operation of the alternator free of charge
Since they will have an interest in selling you a new one, they will probably run a free test. Disassemble the alternator and take it to the workshop to have its condition checked.
Advice
- When the weather is very cold, turn the headlights on for a minute or two before starting the engine and then turn them off. A hot battery will always be able to start a cold car.
- Even if you come to the conclusion that the alternator is not working, be aware that the problem may have another source. For example, a fuse may have blown, there may be a contact on some electrical wire, or you may have a faulty relay or voltage regulator problem.
Warnings
- Keep your hands, clothes and accessories away from moving parts when working inside the hood with the engine running.
- Some recommend testing the alternator by starting the car and disconnecting the negative battery cable, and then wait and see if the engine stops or not. Avoid following this method, as it could cause serious damage to the voltage regulator, alternator, and other electrical components.
