The alternator is one of the most important parts of your vehicle and is often overlooked by drivers. When you think of what makes your vehicle run you often consider two different parts: the battery and the engine. Gasoline fuels the engine which makes your car run, and the battery is what makes the electrical parts go, right? While that is a very basic understanding of how your car works, it misses out on a lot which includes the alternator.
The battery of your car is what kicks off its ability to even start by providing power to the starter and the spark plug which will spark your initial combustion reaction and get your engine moving. Once your car is going the battery takes a backseat to the alternator.
In technical terms, the alternator in your vehicle converts mechanical energy, which is generated by the serpentine belt that connects it to your engine, into electrical energy. That electrical energy charges the battery in your vehicle and also supplies power while your vehicle is running to all the electrical systems. So, your radio, your air conditioner, your power windows, your lights, all of these things are powered by the alternator when your car is in motion. If you did not have a functioning alternator in your vehicle your battery would be able to power these parts for a very limited amount of time but would soon die. It just doesn't have the capacity to meet the electrical demands in a vehicle over a long period of time. To put that in perspective, without an alternator your battery would not be able to power your car for more than 30 to 60 minutes.
As you can see, your alternator has a very important job for keeping your car going. However, it's subject to problems just like any other part of your vehicle and can potentially wear out over time. There are some signs that you can be on the lookout for to let you know if your alternator is giving you some problems.
Signs and Symptoms of a Bad Alternator
It can be difficult to distinguish the difference between a problem with your battery and a problem with your alternator if you're not sure what to look for. Just remember what we said before that the battery starts your electrical systems working but your alternator is responsible for keeping them working. That difference is key to understanding the signs of your alternator when it starts giving you trouble. With that in mind, here are some of the symptoms you can be on the lookout for.
Flickering Headlights: One of the easiest to notice signs that you have a problem with your alternator is how it affects your headlights. When your car is running, your alternator is responsible for powering the headlights. If you notice your headlights are dimming or flickering while your car is running that's a good sign you're having an issue with your alternator. You can further distinguish this as being separate from a problem with your battery if when you first put the key in the ignition to turn your car on your headlights appear bright and strong and then once you get your car running they begin to dim. That's the power switching from your battery which is still strong to your alternator which is giving you problems.
Dead Battery: As we have said, your alternator is responsible for charging your battery while your car is in motion. Your battery can't handle the power requirements of your entire vehicle on its own. A typical car battery has a lifespan of about 3 years to 5 years. If your battery is still in the prime of its life, which is to say that is under that 3-year mark and you know it should be working fine but it still dies on you, you may want to check your alternator as a likely culprit. If it's unable to charge your battery, even a brand new battery is going to fail on you very quickly.
Indicator Light: Just like the check engine light on your dashboard you should also have an indicator light on your display that lets you know you're having a problem with your alternator. Usually this one takes the form of the letters ALT or GEN. If you see either one, it's letting you know that there is an issue with your alternator, and you should get it checked out sooner rather than later.
Consistent Electrical Problems: Again, this is where a newer car owner might think that they're having battery problems when in fact the issue is with the alternator. If your car is running and you're having problems with any systems that run on electricity, which would include your radio, your power windows, power door locks, and so on, then you're likely experiencing a problem with your alternator.
Any one of these components could have their own individual problems, for instance your power windows could have an issue with an actuator in the door, but if you're experiencing issues with two or more of your electrical components at the same time that don't seem to be related to one another, it's most likely a problem with the alternator.
Engine Stalling: Although we tend to think of the engine as running solely on gasoline, you do need to remember that electricity plays an important role in the overall function of your engine. Specifically, as you’re in motion, the alternator generates the power that creates the sparks from your spark plugs. When your alternator begins to fail then your spark plugs won't be sparking when they need to. That means the fuel and air mixture in your combustion chamber won't be igniting when it's supposed to, and your engine will be unable to power your vehicle properly. If this happens consistently, you're going to be experiencing engine misfires and potentially your engine will stall or shut down on you completely. If it gets bad enough your car will shut down and won't be able to get going again.
What Causes an Alternator to Fail?
When it comes to your alternator failing on you there are a number of reasons that it could have gone bad in the first place. To start with, your alternator is powered by a serpentine belt which is attached to your engine. As the crankshaft in your engine turns it rotates the serpentine belt which powers the alternator. If your serpentine belt were to fail in any way, then your alternator would suffer as a result.
Bad Diodes: It's also possible that you have some bad diodes in your alternator which have caused it to fail as well. These are part of what is known as a rectifier assembly which is responsible for converting the AC output from an alternator into DC current. This in turn is what charges your battery. The charging output goes through 6 diodes before it makes it to your battery. If one of these diodes was bad, then it would cause problems with the way your alternator functions. They could burn out over time if you are putting excess strain on your car's electrical system and you aren't driving your car on a regular basis.
Overheating: Your alternator is subject to failing on you when exposed to too much heat. Like we said, if the diodes are taxed too much they will fail and part of the way this happens is by overheating. Other parts of your alternator such as the internal voltage regulators can also fail if they're subject to too much heat, too. That can be both heat from an overheating engine or from external heat just because you live in a hot climate, and from an overtaxed alternator all working together to put too much stress on that part.
How Long Does an Alternator Last?
Typically, an alternator doesn't really require any kind of routine maintenance to keep it functioning. It's meant to last the life of your vehicle and you should be able to drive for 10 years to 15 years with no problems from your alternator whatsoever. Of course, any part of your vehicle is subject to failure either because of the way you drive your car, potential mechanical failure that was unforeseen, and if you are running a high number of electrical components in your vehicle on a regular basis which will put extra stress on the alternator from day to day.
Can You Drive Your Car with a Bad Alternator?
If you're experiencing signs that your alternator is failing on you then you're going to want to get it repaired as soon as you possibly can. In terms of whether or not you can drive with a bad alternator it's a bit of a hard question to answer. You can technically drive for a while with a bad alternator depending on the nature of the problem you're experiencing. For instance, if you have a burnt-out diode, then perhaps your alternator is just only going to be underperforming rather than not working entirely. That will cause problems with your electrical systems, but it may continue to provide power for a while. But that also means you're taxing the rest of the diodes which will burn out much more quickly as a result and lead to your alternator failing entirely.
If your alternator is not working at all, then you will not be able to drive your car. If the alternator were to completely die in the middle of driving, your battery would be able to take over for an extremely short period of time in a limited capacity. You might have enough time to get yourself from wherever you are to a mechanic to get it fixed but, as we mentioned earlier, your battery probably only has the ability to keep your car's electrical systems running for a very short amount of time without the alternator backing it up. The more electrical components your vehicle is running, if you have the radio on, the lights on, the air conditioning running, and so on, the more quickly your vehicle is going to die on you. If your alternator and your battery are both dead, then you will be completely unable to use your vehicle and will need to be towed into a mechanic at that point.
Alternator Repair Cost
If your alternator has died on you completely and you need to get it fixed, your only real option here is to get a replacement rather than a repair. The replacement alternator is not a cheap fix by any means. If you're looking for a brand-new alternator to replace the old one your cost could end up running you anywhere from $400 to $1,000. Most average vehicles will be on the lower end of that scale, but if you have a higher end or rare vehicle you could end up spending upwards of that $1,000 that we mentioned.
If you're interested in simply buying the part itself, AutoZone lists alternators for between about $170 and $400 a piece. When you factor in the labour cost you can see where you could be getting up to $500 or more to repair one of these.
The Bottom Line
Your alternator and your battery are the two key components for ensuring the electrical systems in your vehicle run smoothly every time you get in your car. Consider your battery almost like a backup that supports the alternator when you’re in motion. Your alternator really has to do all the heavy lifting in terms of electrical systems in your vehicle to keep things running. When it has a problem, your entire car has a problem and will not function for very long if you can't get your alternator fixed.
While your first instinct may be to blame the battery when you're having problems with the electrical systems in your vehicle, just remember that the battery just gets it started but the alternator is there to keep everything going. If you can get things started, then the battery is probably fine, and the alternator is to blame. Still, it's always best to go in and have a mechanic take a look when things start to go wrong so you can get to the root of the problem and solve it before a bad situation gets worse.