Updated at: 05-04-2022 - By: micdot

In order for your car’s electrical components to function, the alternator must be working. This page explains in detail how to check your alternator for problems.This author has been thoroughly vetted and is qualified to write about this subject matter. Learn more about us by visiting our website’s “About Us” page.There is an alternator in your automobile, which keeps your battery charged and guarantees that the various systems of your vehicle have enough power.Here’s how to check an alternator if you’re concerned about its performance.A deeper understanding of automobile alternators can only be achieved by beginning with the basics.

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What Is An Alternator?

What an alternator is and what it accomplishes can help you understand why an alternator should be tested.The battery is commonly thought of as the source of power in a car, and this is correct. Nevertheless, an alternator is necessary for the many electrically driven components of the vehicle.There are two primary functions of an alternator: to recharge the battery and to supply power to electrical devices. The engine’s mechanical energy is converted to electrical energy in this process.You can start your car thanks to the battery’s ability to store energy. Without an alternator, your battery would be completely depleted in a matter of hours because it would be the sole source of power for your vehicle.

How Does An Alternator Work?

There is a belt attached to the alternator to keep it running smoothly. The engine, and more specifically the crankshaft, drives the belt.The rotor inside the alternator is likewise moved by the belt’s movement. Electromagnetic induction generates voltage when the rotor spins.Moving belt energy can be converted into electrical energy by a rotating portion of the alternator.An alternator’s basic concepts are illustrated in a brief article from the BBC.

How to Test an Alternator - YouTube

Signs Of A Broken Alternator

Numerous indicators point to a malfunctioning alternator. The good news is that alternators are meant to last for the life of the vehicle, so a broken one is extremely rare.The alternator can fail for a variety of reasons, including, but not limited to, those listed above. The following are symptoms of a bad alternator:

Fluffy light bulbs

burning rubber is in the air.

Mistakes in electrical systems

Inability to get off the ground/regular stopping

Batteries are no longer charging

Warning lights on the battery

A strange sound

Each of these signs and symptoms will be examined in more detail later on. Although alternator failure is extremely unusual, it may be remedied reasonably quickly and cheaply if it does occur.

Flickering Lights

When the engine is running, the alternator should provide reliable power. Flickering or dim lights are likely if your car’s alternator isn’t working properly for some reason.This is due to the alternator’s inability to maintain a constant voltage level. This may be due to an issue with the voltage, which may cause the headlights to become brighter or dim.The headlights will flicker if the voltage output is irregular, and this is due to the imbalance.

Smell Of Burning Rubber

An alternator’s serpentine belt is comprised of rubber reinforced with fiberglass. A burnt rubber odor could be coming from the serpentine belt if it is malfunctioning in any way.Even if the serpentine belt is damaged, the alternator itself may be defective, resulting in the same type of odor. A weird whining sound may indicate that the alternator is to blame for the problem.There’s a chance you’ll catch a whiff of smoke from an electrical fire. Due to either an excessive quantity of electricity being generated or insufficient cooling, the alternator may overheat.Take your car to a repair immediately if you detect the odor of an electrical fire. Avoid inhaling the poisonous fumes it may emit. Burning rubber can be caused by a variety of factors.

Reasons Why Your Car Smells Like Burning Rubber and How to Fix It |  CarCareHunt

Electrical Malfunctions

The alternator in your automobile provides power to virtually all of your vehicle’s electronic components, including your power windows, radio, power steering, wipers, and so on. Your car’s electrically powered components may not perform properly if the alternator is found to be defective.Despite the fact that this isn’t always the case, there may be other signs. As an example, your windows may not retract smoothly or at a much slower pace.

Starting Difficulties/Frequent Stalling

The battery is most likely to blame for a tough time starting your car. However, a malfunctioning alternator could also be to blame.If the alternator fails to function properly, the battery will not be able to be recharged, resulting in its depletion. Find out if the problem is with the battery or the alternator by continuing to read.Your spark plugs could be the problem if you can start your automobile but it keeps stalling. The spark plugs aren’t working properly since your alternator isn’t delivering enough power on a regular basis.

Dead Battery

Your battery will run out of power within an hour or two if your alternator isn’t working. Because it can’t charge, the battery will eventually die.It is common for individuals to think that the battery is to blame when a device no longer functions properly. Even if that is the case, as it often is, the alternator needs to be checked.It is the alternator, not the battery, that is to blame if the battery fails and is replaced, only for the replacement to fail within a few days or weeks. If your battery is losing power at an exceptionally rapid rate, be careful to check your alternator. This is a time and money saver.

Battery Warning Light

It’s not just when your battery is low that the battery warning light comes on, but when the alternator’s voltage output is irregular. The warning light can also flicker for the same reasons your headlight does. Your battery is most likely failing if the warning light comes on when you start the car but goes out while you are driving. At the very least, your alternator is now operational!

When you turn on the air conditioner or your high beams in your automobile, you may see a battery warning light come on. Your alternator must be able to keep up with the demand for those functions, which means it must be running efficiently.

What Does the Battery Light on the Dashboard Mean? | HowStuffWorks

Abnormal Noise

An untrained ear is often baffled by the noises coming from the engine area. The fact that a malfunctioning alternator can make a variety of noises, each indicating a different underlying problem, does not help matters. Wailing and high-pitched noises are common signs of a malfunctioning alternator. The bearings of the alternator or the serpentine belt may also make a grinding or squealing noise.

How To Test An Alternator

It’s time to find out how to test your alternator now that you’ve seen the most typical symptoms and understand what an alternator is.

Measure The Volts

Volts are everything when it comes to alternators. Using a multimeter or voltmeter, you can determine how effective your alternator is. You only need to follow these instructions:

1. Measure Your battery

Check the battery’s condition first. When the battery is turned off, the voltage should be between 12 and 13 volts. Ensure that your battery has a voltage of at least 12 volts before using it.

2. Turn On The Engine

Start the engine and record the readings from the voltmeter or multimeter you have connected to the battery connections. Your alternator is in good working order if the voltage reading is between the mid-high 13s and the mid-14s.

3. Turn On Electrical Accessories

Make sure your readings are correct, then leave the voltmeter attached to the battery and turn on all of the vehicle’s comfort features including the air conditioning and heating. A faulty alternator will cause the voltage to drop below 13 volts when any of these characteristics are active at the same time.


You may need to replace your alternator if the voltage readings fall outside of the reference ranges provided in the stages above.

Test The Serpentine Belt

How To Properly Check A Serpentine Belt - YouTube

You can quickly test the pulley if you suspect a problem, such as a squeaky noise, is present. If the engine is hot, wait for it to cool down. While the engine is off, simply grip the alternator belt and pull it downwards. The alternator may need to be replaced if you continue to hear this squeaky noise.

Inspect The Alternator

Loose nuts or misaligned belts might cause unusual noises to come from the alternator. Look for any loose or damaged pieces and give it a thorough check.


A car’s battery is frequently the only source of power for the vehicle’s electrical components. The alternator, on the other hand, is a key component. Batteries fail all the time, but alternators rarely do as well. Among the warning signals that your alternator is malfunctioning include flickering headlights, a burning rubber odor, and other electrical issues. If you have any reason to believe your alternator may be malfunctioning, stay off the road. The problem can be easily diagnosed if you have a voltmeter or a multimeter.