Having a vehicle that isn’t operating properly — or not operating at all — can be frustrating, and it’s difficult to figure out what the issue is and what it might cost to fix. We’ve broken down what an alternator is, how to know if yours is bad, and what to expect when you need it replaced.
What is an alternator?
Your car's alternator generates most of the electricity in your vehicle, powering everything from the radio to taillights. Here’s how it works:
- Your vehicle’s engine spins a belt that’s attached to the alternator via a pulley system.
- This pulley rotates the alternator’s rotor shaft and a surrounding set of magnets that pass around a coil, generating a current.
- This alternating current (AC) is channeled into the rectifier, which converts it to the direct current (DC) needed to run your vehicle’s electrical systems and recharge your car battery.
Your car battery stores the excess electricity created and saves it for when you need power while your engine isn’t running, like at start-up. Alternators are a pretty standard piece of equipment in most vehicles, although some hybrid models won’t have one.
Symptoms of a bad alternator
A broken alternator — not to be confused with a failing alternator belt (also called the serpentine belt) — can be hard to diagnose because many of the symptoms of a bad one are the same as the symptoms of a faulty battery, and both can be debilitating enough that diagnostic tests are impossible to run. In layperson’s terms, it’s hard to know what’s wrong with your car’s electrical system when there’s no power.
... many of the symptoms of a bad alternator are often the same as the symptoms of a faulty battery ...”
Here are a few common symptoms of a bad alternator:
- Battery light on dash: If your dashboard is showing the word “CHARGE” or a battery symbol after the battery is turned on, that means there’s a problem with your charging system, not necessarily your actual battery.
- Dead battery: A faulty alternator won’t properly charge your battery while the engine is running, so a dead battery could be a sign of an alternator problem. The best way to tell if it’s your battery or alternator is to jump-start your car. If it dies soon after the jump-start, it’s likely your alternator and not your battery.
- Difficulty starting: If your car has a hard time starting, it might be caused by your alternator. If the alternator is bad, your battery won’t have the necessary power to start your car.
- Grinding or whirring: If you’re hearing some unexpected noises, like grinding or whirring, it might be due to broken pieces within an alternator. For example, if the bearings in your alternator are starting to fail, the noise produced is usually pretty hard to miss.
- Weakened power supply: Because your electrical components are powered by your alternator, a weakened power supply could be a sign of a bad alternator. Look for things like slow-rolling windows, dimmed headlights or slow windshield wipers.
Regardless of the cause, if you’re experiencing issues with your vehicle, it’s important to schedule an inspection with a licensed mechanic. They can test different components of your vehicle and use OBD-II readings to determine what the issue is. You’ll have to pay for these tests, but they should help you avoid paying for a repair that’s not needed.
How much does it cost to repair an alternator?
Repairing your vehicle's alternator generally isn’t a viable option compared to replacing one. There are a few reasons for this, but the main one is that repairing something can cost a lot more in terms of labor than replacing it.
- An alternator repair can require a diagnosis, removing and disassembling the existing alternator, installing new components, testing them, and reinstalling the alternator.
- An alternator replacement is as simple as buying a new alternator, taking out the faulty unit and putting in the new one.
In theory, an alternator repair could be cheaper, especially for high-end vehicles, but it’s uncommon. If you want to explore all of your options, ask your mechanic for an itemized repair quote and compare it to the cost of a replacement. An itemized quote will allow you to see exactly what you’re paying for and how much of it is related to labor and how much is related to parts.
How much does alternator replacement cost?
We gathered estimates for replacing an alternator in three sample vehicles in Austin, Texas, to give you examples of what this service might cost. The costs for replacing an alternator in these sample cars range from roughly $530 to $2,660.
|Vehicle||Parts cost||Labor cost||Total cost|
|2016 Honda Civic||$427.01 to $733.92||$164.27 to $223.24||$591.28 to $957.16|
|2016 Ford F-150||$447.09 to $768.44||$82.13 to $111.62||$529.23 to $880.06|
|2018 BMW 740i||$1,227.88 to $2,110.42||$401.54 to $545.69||$1,629.42 to $2,656.10|
*Estimates gathered from AAA’s car repair estimate tool.
Your vehicle’s make, model and age affect the cost of repairs. Newer, higher-end vehicles tend to have more expensive components, while less expensive vehicles are likely cheaper to fix.
Rebuilt alternators for our sample vehicles can cost as little as $200.
Our parts estimates are also in line with prices for components from the original equipment manufacturer (OEM), but you can potentially save a lot of money by using aftermarket parts. Just be aware that this may affect whatever warranty is left on your vehicle.
Labor costs vary less across our sample cars, but these still differ from vehicle to vehicle. Some cars and trucks have more compact or complicated setups under the hood that make it harder to get to the alternator, and the more time it takes to replace your alternator, the more you’ll pay.
Can I drive with a bad alternator?
You can potentially drive a short distance with a faulty alternator, but we don’t recommend it. Because this component powers so many different parts of your vehicle, driving with a bad alternator can impact various functions. A faulty alternator often leads to a dead battery, but if left unfixed, it could ruin your car battery too.
Simply put, you and your wallet are probably better off getting a bad alternator replaced before it leads to more extensive issues.
Frequently asked questions
- How long is an alternator supposed to last?
- An alternator should last around six to 10 years, depending on how much you drive and what kind of car you have. If your vehicle has extra electrical components that are used regularly, your alternator’s life span can be even shorter, though.
- What do you do after replacing the alternator?
- After an alternator is replaced, there are tests you can run to see if it’s working correctly, but the simplest way is often to drive it like normal and see if you encounter any problems.
Alternators don’t usually need any maintenance, so you shouldn’t have to worry about it again for some time.
- Do extended car warranties cover alternators?
- It depends. Base-level coverage might not cover your alternator, but if the extended auto warranty covers your car’s electrical system, the alternator is usually included.
- Does car insurance cover alternators?
- Not usually. Alternators don’t often break due to accidents or vandalism, which means the cost to replace this component probably won’t be covered by auto insurance.
- Article sources
- ConsumerAffairs writers primarily rely on government data, industry experts and original research from other reputable publications to inform their work. To learn more about the content on our site, visit our FAQ page.
- AAA, “Estimate Car Repair Costs.” Accessed August 17, 2021.
- Nationwide Insurance, “What is an Alternator?” Accessed August 20, 2021.
- Firestone Complete Auto Care, “What Does An Alternator Do?” Accessed August 20, 2021.
- The Drive, “What Is the Average Lifespan of An Alternator?” Accessed August 20, 2021.
- Auto Services Cost, “Alternator Replacement Cost.” Accessed August 20, 2021.
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