How to Perform an Alternator Replacement (+Cost)

Car struggling to start?
Before you blame the battery, consider that a faulty alternator could be the culprit here.

The alternator is the powerhouse that keeps your battery charged and runs every essential component, from your headlights to your radio. But if it starts acting up, you need to change it ASAP.

Wondering how an alternator replacement works?

Read on to discover the ins and outs of an alternator replacement and how much it’ll cost you. We’ll also highlight a few red flags of a failing alternator to help you spot one before it leaves you stranded.

This Article Contains:

What Are the Signs of a Bad Alternator?
How to Replace an Alternator? (A Step-By-Step Guide)
How Much Does It Cost to Replace an Alternator?
5 FAQs Related to Alternator Replacement

What Are the Signs of a Bad Alternator?

Your faulty alternator may exhibit these symptoms:

Car won’t start: Whether you own a Toyota or Ford, the first sign of a bad alternator is often a car that won’t start due to a flat battery. That’s because starting an engine puts a significant load on the battery, and if the alternator is damaged, it won’t be able to supply enough voltage to recharge it. This results in a dead battery.

Grinding noise: Worn-out alternator bearings may cause a grinding or whining noise. You might also hear a whining noise when the voltage regulator signals the alternator to overcharge or because of a bad alternative pulley.

The smell of burning rubber: When the alternator overheats or fails, it may cause the rubber belts to burn. Damaged or malfunctioning internal parts, like wires or insulation, can also smell like burning rubber.

Sluggish accessories: A failing alternator won’t supply enough power to your vehicle’s electrical components, resulting in slow or non-functional accessories. For instance, your power windows may roll up slowly, or the cooling fan might run at a lower speed.

Dim or flickering lights: An insufficient electrical charge from the bad alternator can cause the interior lights and headlights to flicker or glow dimly.

Active dashboard warning light: Sometimes, the battery light on your dashboard may also activate due to a faulty alternator instead of a failing battery. This happens when the alternator is unable to charge the battery.

Next, we’ll cover in detail how to change a bad alternator if you have one.

How to Replace an Alternator? (A Step-By-Step Guide)

Before you begin an alternator replacement, ensure your battery is fully charged. Don’t use the new alternator to charge a low battery, as it can affect the alternator’s internal parts.

Important: Alternator replacement is more complicated than other services, like tire repair, and requires automotive expertise. So, it’s best to book an alternator replacement service instead of attempting a DIY.

Let’s look at a few special tools your mechanic will use for the job.

Tools Needed:

Belt tensioner
Replacement serpentine belt
Battery tender or memory saver (optional)
Voltmeter
Essential hand tools (sockets, ratchets, and wrenches)
Rags, gloves, and safety gear
Jack, jack stands, and wheel chocks (if required)

Here’s how a mechanic will replace a failing alternator:

1. Disconnect the Battery

First, the auto mechanic will turn off the ignition and disconnect the negative terminal of your car battery. This prevents any circulation of electrical energy through the vehicle’s electrical components.

2. Locate and Test the Alternator

An alternator can be identified by its aluminum body, vents, and an operative cooling fan. It’s usually bolted to the front or side of the vehicle’s engine. In some cars, the mechanic may access the alternator from underneath the vehicle using tools like a hydraulic jack, jack stands, wheel chocks, etc.

Your auto repair mechanic will also use a multimeter to check the battery and determine if you need a car alternator replacement.

Here’s how they’ll test the alternator:

Turn off the vehicle and wait a few minutes for an accurate reading.

Ensure that the car battery terminals are clean.

Switch the multimeter to the 20 DC volts (DCV) setting.

Attach the multimeter’s black probe to the negative battery terminal and the red probe to the positive terminal. Your vehicle battery’s resting voltage (the voltage of a car battery when the engine is off) should be around 12.6V. A lower reading indicates that something is draining the battery.

They’ll do the same test on the battery but with the engine running. The output for the car battery now should be between 13V and 14.5V. Any reading over or under this range indicates the alternator is overcharging or undercharging the battery.

They’ll verify the other signs, like slow accessories, to confirm the alternator issue.

While replacing the alternator, the mechanic will inspect every other essential component of the vehicle’s charging system. These include:

Drive belt (serpentine belt): The alternator converts the mechanical energy generated by the serpentine belt into electrical energy. They’ll look out for cracks, frays, and other wear signs on the drive belt and replace it if needed.

Drive belt tensioner: The belt tensioner must not be excessively tight or loose. They’ll also check the alignment of the drive belt and alternator pulley.

Electrical connections: They’ll check that all alternator pigtail connectors, wires, and harnesses are clean and intact. This will ensure an adequate flow of electrical energy to every electrical component.

Battery terminal B+ voltage wire: If the alternator’s battery wire looks burnt, melted, damaged, or stiff, your mechanic will replace it.

Contaminants: They’ll look for oil, grease, or antifreeze contamination on the alternator’s aluminum body and surrounding areas.

Car care tips: Regularly wipe down your engine and the alternator case with a light solvent to keep them clean and free from dirt, dust, or debris.

4. Remove the Bad Alternator

Once they’ve inspected and replaced every faulty electrical component, the mechanic will disconnect and unbolt the alternator from the vehicle’s engine and mounting brackets.

5. Compare Both Alternators

The mechanic will compare and ensure all components of the old alternator match the new one, including the electrical connector plug-in position and mounting bolt holes.

Note: Due to manufacturer consolidation, some alternators may look different. Your mechanic will check the installation paperwork for the new alternator to confirm it’s the right one.

6. Install the New Alternator

Once confirmed, they’ll install the new alternator, drive belt, and electrical connections. The mechanic will also scan their surrounding areas to ensure nothing is overlooked.

They’ll install new felt washers on the battery posts and reattach the battery cables. Additionally, the mechanic will apply battery post grease to prevent future acid buildup and corrosion.

Wondering how much an alternator replacement could set you back?
Keep reading!

How Much Does It Cost to Replace an Alternator?

The alternator replacement (including the replacement parts) can cost anywhere from $200 to $1200. You can expect to pay around $100 to $1000 for a new alternator and $100 to $200 for labor charges. If the serpentine belt also needs a replacement, you’ll have to pay an additional $90-$200.

Remember that the parts and labor costs for alternator replacement services also depend on the type of vehicle you drive.

For instance, some alternators are easier to replace than others based on their location in the engine bay. Generally, the lower the alternator sits, the more engine components need to be removed to access it.

That said, most experienced technicians will complete this auto service in an hour or two, including the initial testing and diagnosis.

If you still have doubts about your alternator replacement, the following section will help tackle them.

5 FAQs Related to Alternator Replacement

Here are answers to commonly asked questions about the alternator:

1. How Does an Alternator Work?

The alternator uses a drive belt and a couple of pulleys to convert mechanical energy from the engine into alternating current output via the alternator’s stator.

A rectifier, an electrical device inside the alternator, converts this alternating current output into direct current, activating your car’s electrical system. By doing so, the alternator, along with the voltage regulator, helps power accessories like headlights, electric power steering, power windows, etc.

2. Can You Fix a Bad Alternator?

When an alternator issue occurs, it’s best to replace them rather than go for an alternator repair.

That’s because repairing the internal parts of a bad alternator can cost almost as much as an alternator replacement service. Additionally, a new alternator will last longer than a refurbished one and usually comes with a warranty.

However, in some circumstances, it makes more sense to schedule a repair. This includes replacing a worn drive belt, bearings, voltage regulator, diodes, loose or frayed wiring, etc.

Car care tips: Ask your mechanic to check your drive belt during your car’s annual preventative maintenance. This can help prevent the alternator from overworking and wearing out faster.

3. How Long Does an Alternator Last?

Most alternators typically have an average lifespan between 80,000 and 150,000 miles before you need alternator replacement services. This generally translates to about seven years of use.

4. Can a Car Run with a Bad Alternator?

No, you shouldn’t drive a car with a failing alternator.

A failing alternator won’t be able to recharge the battery sufficiently. So, if you’re driving and the engine dies or stalls, the battery may not provide enough electricity to power the starter and crank the engine, leaving you stranded. This is particularly dangerous if it occurs at an intersection or on a busy road.

So it’s best to book an auto service if you start noticing the signs along with an active dashboard warning light.

5. How to Tell if it’s a Bad Battery or a Bad Alternator?

Here’s a surefire way to test if you have a bad battery or an alternator problem:

Connect a running battery to your car’s battery using jumper cables.
Let it charge for a couple of minutes, then try starting your vehicle.
Once it starts, remove the jumper cables. If your engine stalls, your alternator has probably gone bad.
If it continues to run, your battery needs a replacement.

Opt for Reliable Alternator Services with AutoNation Mobile Service

Driving with an alternator problem is dangerous and could even get you stranded. However, testing and replacing an alternator on your own can be risky without the necessary technical know-how.

That’s why you should get your alternator inspected and replaced by an expert at AutoNation Mobile Service.

We’re a mobile auto repair service available seven days a week for any repair and preventative maintenance. We also offer a 12,000-mile, 12-month warranty on every kind of car repair, whether you drive a Honda or Hyundai.

Contact us for alternator replacement or other services like brake repair or suspension repair from your driveway.