Not sure if your alternator is in good condition? It's hard to tell if an alternator is working properly if you have no idea how to check it. The simplest way is by testing it with a voltmeter. If you know your car well, there are a few methods you could use. This test is to give you a general idea of the condition of your alternator and battery. Some newer vehicles come integrated with computer controlled charging systems and may need further testing.
Method 1 of 2: Use the voltmeter
Step 1. Buy a voltmeter
Find one at any auto parts store for under $ 20. Don't rush to buy the most expensive one; a cheap voltmeter will help.
If you have a multimeter, it will do the trick too. A multimeter also measures voltage, as well as other electrical properties, such as current and resistance. What you want to do is measure the voltage while checking the alternator
Step 2. Check the battery first
The battery is required to start the vehicle, which in turn rotates the alternator at an effective speed to keep the battery charged. This means that if your battery is low, you will not be able to start the vehicle, and therefore, you will not be able to test the alternator either, making any other test with the voltmeter useless. If it's cold outside or your battery is old, the problem may be the battery itself and not your alternator. This is why you need to check the battery before moving on to the alternator. Here we tell you how to do it:
- Turn off the engine. You'll want to make sure your engine is off before connecting the voltmeter.
- Open the hood.
- Connect the voltmeter to the battery. Connect the red terminal of the voltmeter to the positive terminal of your battery and the black terminal to the negative terminal. Prevent your skin from coming into contact with the battery
- Look at the voltmeter. If the battery shows a reading greater than 12.2 volts, it means that it has enough charge to start the alternator and test it consecutively with the voltmeter.
- If the battery does not have enough voltage, you have the option of recharging and re-measuring or trying a different method to test the alternator.
Step 3. Start the vehicle and rev it up to 2000 rpm
This will drain power from your battery, causing the voltage regulator to force the alternator into full gear.
Step 4. Keep the engine running and retest the battery with the voltmeter
When you see the measurement this time, the voltage should rise to 13 volts. If the variation of revolutions per minute causes the voltage to fluctuate between 13 and 14.5 volts, it means that your alternator is in good condition. If, on the other hand, the voltage remains the same or decreases, it means that your alternator is not working properly.
Repeat the same process, but now with the lights, radio and air conditioning on. If the battery voltage remains at 13 volts with the engine at 2000 rpm and all accessories on, it means that the alternator is charging it
Method 2 of 2: Check Your Alternator
Step 1. Check the alternator gauge
If you have a volt / amp meter, it will measure the values for you. Crank the engine to 2000 rpm to test it, turn on the air conditioning or heater fan, headlights, and any other accessories that put the alternator to work. Check the meter to see if there is any drop in voltage or amperage. As a rule of thumb, if the volt count is higher when the engine is on than when it is off, rest assured that the alternator is recharging.
Step 2. Listen to the alternator with the engine running
If there is a problem with the bearings, you may hear a screech in the front of the car, becoming louder if you have other electrical accessories consuming power at the same time.
Step 3. Turn on the radio and rev up
Turn on your radio at a low amplitude modulated (AM) frequency without music. If the radio screeches or is fuzzy when you step on the accelerator, the alternator is most likely to blame.
Step 4. Find an auto parts store that will test alternators for free
Since stores want you to buy a new alternator from them, they will try to get ahead of their competitors by offering you a free trial. Uninstall your alternator and take it with you to make sure.
- If it is very cold outside, before starting the car, activate the headlights for 1 or 2 minutes and then turn them off. A hot battery will always start a cold car.
- Even if you conclude that the alternator is not working, the problem could have originated elsewhere. Maybe you have a blown fuse, a bad relay, or a bad voltage regulator.
- Keep your hands, loose clothing, and jewelry away from moving parts when inspecting under the hood overhead and with the engine running.
- Some people recommend testing the alternator by starting the car, loosening the negative battery cable, and waiting to see if the engine shuts down or not. Do not try this method, as it could fry the voltage regulator, alternator, and electrical components.