How Long does an Alternator Last?


When drivers think about the electrical power of their vehicle, they often think about the car battery the most. However, the battery produces the least amount of power for a vehicle. It is the alternator which is really in charge of powering the main electrical accessories and features of a vehicle, such as its radio, air conditioner, lights, and so on.

All the battery does is produce the electrical charge needed for the ignition to take place when you start the vehicle. After that, the battery may serve as an electrical reserve in case something goes wrong with the alternator’s power flow. But overall, the alternator is the king of a car’s power source. It is the component that keeps the car running after the battery helps start the engine.

Alternators certainly last longer than car batteries. Auto manufacturers tend to provide different answers when it comes to the question of an alternator’s life expectancy. On average, you can expect your car alternator to last between 4 and 7 years. But it really depends on how often you drive and how many miles you put on your vehicle. For most drivers, they need to replace their alternator every 40,000 to 80,000 miles. Some car manufacturers may claim their alternators last over 100,000 miles, but that is not typical. People who purchase a new car tend to have alternator problems after the 50,000-mile mark.

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Notice the Symptoms of a Failing Alternator

It can be tricky to know when your alternator is failing. The symptoms of a failing alternator are almost identical to the symptoms of a failing battery. That is because they are both important power sources for your vehicle. You cannot have one working power source without the other. They both rely on each other to allow the vehicle to run properly.

To tell the difference, here are the common symptoms of a failing alternator:

1) Flicking Lights – Flicking lights are the first indicator that your alternator may be failing. Sometimes this can happen when the battery is going dead. But, remember that the alternator is the main power source of your car lights and electronic features. If you test your power windows or radio and they’re functioning slowly or abnormally, then you can blame it on your alternator.

2) Dead Battery – If you start experiencing electrical problems, test the car battery with a multimeter. This instrument can let you know the current voltage of the battery. If there is little to no voltage, then it is obviously a dead battery. This can happen when the alternator dies, and the battery is forced to provide all the power for the vehicle. Within minutes, the battery will lose all its power too because it cannot handle these power demands by itself. If you have a relatively new battery that is under 2 years old and it has gone dead, then it is likely because of a bad alternator.

3) Engine Stalling – The internal combustion engine may stall if there is an alternator problem. Since the fuel injection system depends on electrical power from the alternator, then a bad alternator will slow down the fuel injection system. This, in turn, slows down the engine because the injectors can no longer inject enough fuel into the engine to allow it to generate sufficient power.


Pay close attention to the mileage of your vehicle and the number of years you’ve had your battery and alternator. Using this information alone can usually help you figure out whether the alternator or battery has gone bad. But be aware that if you replace your alternator at an auto shop, they may give you a used alternator as a replacement. Because of this, the used alternator will last about 2 to 4 years instead of 4 to 7 years. Keep that in mind.


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