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Symptoms of a Bad Alternator & How to Diagnose It

CarPart  ·  October 16, 2021

Symptoms of a Bad Alternator & How to Diagnose It

In a car, most people think that only the battery powers all the electrical components. However, this is not the case. The alternator is also an essential part when it comes to a car’s power supply.

So, What’s an Alternator?

An alternator, aka generator, is a component that keeps the car battery charged. Engine power is conveyed to the alternator through the engine drive belt known as the serpentine belt. 

The alternator charges the battery by first converting mechanical energy into a current, which it then sends to the battery.

Keeping the battery fully charged makes it possible to power the headlights, heater, car stereo, navigation, and other electrical systems. 

So, you see, an alternator is a very crucial component, and you need to know when it is malfunctioning so that you can fix it immediately.

Signs of an Alternator Going Bad

When an alternator malfunctions or fails, the outcome is a ripple of effects of car problems. The car may even fail to start. To prevent this situation from happening, here are some of the common symptoms of a failing alternator that you should not ignore.

1. Check engine light on

A car's warning indicator light implies that there is a problem. Depending on the car model, when the ‘ALT’ or ‘GEN’ or ‘Check Engine’ indicator (in some cases a battery icon) starts showing up it means your alternator is most likely having a problem. Don’t ignore this indicator light when it turns on. Instead, take the car to an automotive specialist.

2. Dim or flickering headlights

Flickering headlights is a commonly recognised symptom by drivers. The alternator plays a crucial role in providing power to the headlights. So, when they start to dim or flicker, the alternator is most probably failing. There is added certainty to this if the lights turn brighter or dimmer as one accelerates or decelerates. 

3. Strange noises

Much as many other things may lead to odd car noises, it is still worth noting that these sounds may be a result of the alternator not working correctly. A worn-out bearing may create an unusual grinding sound.

Also, the serpentine belt (after operating for a long time) can stretch and will not be able to spin the alternator pulley effectively as it should. As a result, there will be a lack of charge followed by a weird squealing sound. 

4. Difficulty starting the car or the car stalls

The alternator supplies the power to the spark plugs that ignite the fuel and cause combustion. When the alternator begins to malfunction or fails, it may not be able to power the spark plugs. This failure will cause the car to stall or have difficulties starting.

A weak or dead battery might also show a similar symptom, but if you can rule out this possibility, then it is most likely the alternator.

5. Electrical failures

The alternator is a crucial source of electrical power that keeps the electrical systems running. Electrical issues and failures are, therefore, a strong indication that something is not right with the alternator. 

Systems powered by the alternator, such as power windows, power locks, dashboard lights, air conditioning systems, and car stereo may start acting up as a result. The power windows may start to operate slowly, or the car radio stops working suddenly.

While other things can cause these failures, we recommend that you have the alternator checked at a reliable auto repair shop.

6. Weak or dead battery

Car batteries do not hold power for long periods. Without a functioning alternator, the car will use up all the battery charge until it is drained. With a failing alternator, there won’t be any power supply to recharge the battery. 

This will leave the battery drained or dead. It is, however, important to ascertain if it is a weak battery or a faulty alternator. While the alternator keeps the battery charged, it does not keep it going forever. A weak battery is not capable of holding the power supplied to it by the alternator.

To make sure that the battery is not the issue, check the dashboard battery gauge when the vehicle is off. If the dashboard lights are dim, the battery has a problem. Conversely, if it sends a strong charge, then the battery is most likely okay. 

How to Diagnose a Failing Alternator / Generator

Equipment needed to diagnose a bad alternator:

Steps to Follow

  1. When the 'Check Engine' light turns on, connect the code reader to the diagnostic port. If it shows the code P0562, it likely is a failing alternator. You should have it checked before it fails. Note that the code may vary depending on the model or make of the car.
  2. If you don't notice these symptoms but have a feeling the alternator is not working as it should, you can open the bonnet and check the condition of the serpentine belt. A glazed or burnt belt indicates that the belt is slipping. The serpentine belt is easy to replace and not costly; hence replacing it is the viable solution.
  3. If everything looks in order under the hood, take it to the next level and make use of the multimeter. Before carrying this test, park the car on a flat ground with the parking brake turned on. As a precaution, wear safety glasses.
  4. Set the meter at a DC voltage of about 20V and attach the lead to the battery correctly - positive to positive and negative to negative. The meter should show a reading of about 12.6V.
  5. Now start the engine again and check the voltage. If the alternator is working correctly and not faulty, the meter should display a value of about 14.2V. 
  6. Turn the electrical systems on, such as heater and headlights. Recheck the voltage reading, and this time the meter should read 13V.

If the meter displays any of these readings lower than the expected value, it’s time to change the alternator. 

You can also slightly tap the alternator while the engine is running. If charging goes back to normal, then the coals inside it are becoming worn out.

All the same, if you experience any of the above symptoms, you should head to an auto shop and get the alternator checked.

There you have it! Six easy steps to confirm earlier symptoms of a bad alternator. I hope you found this helpful. Please check out our other blogs and find simple DIY hacks for keeping your car in shape!

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