Car struggling to start?
Don’t be so quick to blame the battery!
Your alternator might be the real troublemaker 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.
So, how do you know if your alternator is on its last legs?
And what does replacing it involve?
Stay with us as we explain the replacement process and give you a realistic estimate of the costs involved.
This Article Contains:
- 8 Evident Signs of a Bad Alternator
- How to Replace an Alternator: A Step-By-Step Guide
- Common Mistakes to Avoid While Replacing an Alternator
- How Much Does It Cost to Replace Alternator?
- 5 FAQs Related to Alternator Replacement
8 Evident Signs of a Bad Alternator
Your faulty alternator may exhibit these symptoms:
- Car won’t start: A dead battery due to a failing alternator can prevent your car from starting.
- Dim or flickering lights: Weak electrical charge can cause headlights and interior lights to flicker or dim.
- Active dashboard lights: A faulty alternator may trigger the engine or battery light on your dashboard.
- Sluggish accessories: Power windows, windshield wipers, air conditioning control, and other electrical components may slow down or stop working.
- Grinding or whining noise: Worn-out bearings or a faulty pulley can create unusual sounds.
- Burning rubber smell: Overheating alternators can burn belts or internal components.
- Engine stalling: A failing alternator can drain the battery and fail to power accessories, like the fuel pump, causing the engine to stall.
- Slow cranking: Low battery charge from a bad alternator can make engine startups sluggish.
Now let’s move on to changing a broken alternator.
How to Replace an Alternator: A Step-By-Step Guide
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.
But if you still wish to know how it’s done, let’s look at a few special tools your mechanic will use for the job:
Tools Needed:
- Belt tensioner
- Battery tender or memory saver (optional)
- Multimeter
- Essential hand tools (sockets, ratchets, and wrenches)
- Rags, gloves, and safety gear
- Jack, jack stands, and wheel chocks (if required)
Additionally, they’ll take certain safety precautions to protect themselves and the vehicle:
- Wear insulated gloves and safety glasses.
- Park the car on a flat surface in a well-ventilated area and use wheel chocks.
- Let the car cool down completely.
- Keep a fire extinguisher nearby in case of emergency.
Now, let’s see how a mechanic will replace a failing car alternator:
1. Disconnect the Car Battery
First, the auto mechanic will turn off the ignition and disconnect the negative battery cable from the negative battery terminal of your car’s battery. This prevents any circulation of electrical energy through the vehicle’s electrical components.
They may use a car battery tender or a memory saver to maintain power to the car’s electrical system. This helps prevent memory loss in radios, clocks, and engine settings.
2. Locate and Test the Alternator
The alternator is 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.
Next, your auto repair mechanic will use a multimeter to check the battery and confirm if you need a car alternator replacement.
NOTE: Before a mechanic begins alternator replacement, they’ll ensure your battery is fully charged. Using the new alternator to charge a low battery can affect the alternator’s internal parts.
3. Disconnect Alternator Wires and Intake Manifold
If the intake manifold or radiator hose is obstructing access to the alternator, they’ll detach them first.
Next, they’ll remove the wiring harness and any electrical connector to the alternator, including the main power cable (B+ terminal), voltage regulator connector, and ground wires.
4. Remove the Drive Belt
Using a wrench or serpentine belt tool, they’ll rotate the drive belt tensioner to release tension on the belt. The belt tensioner must not be excessively tight or loose. They’ll also check the alignment of the drive belt and alternator pulley.
NOTE: Older cars may have a separate alternator belt instead of a serpentine belt.
Then, carefully slide the belt off the alternator pulley while keeping an eye on its path around other pulleys. They’ll look out for cracks, frays, and other wear signs on the drive belt and replace it if needed.
5. Check All Electrical Connections and Remove the Old Alternator
The mechanic will inspect all alternator pigtail connectors, wires, and harnesses for damage. If the alternator’s battery wire looks burnt, melted, damaged, or stiff, your mechanic will replace it. This will ensure an adequate flow of electrical energy to every connected component.
They’ll look for oil, grease, or antifreeze contamination on the alternator’s aluminum body and surrounding areas, which may have contributed to an electrical problem.
Once they’ve inspected and replaced every faulty electrical component, the mechanic will remove the alternator from its mounting brackets by loosening each mounting bolt. They’ll also clean the mounting bracket since the alternator is grounded through the bracket. They’ll clean every bolt too.
6. 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 holes for mounting bolts.
6. Install the New Alternator
Once confirmed, they’ll install the new alternator, tighten its mounting bolts, and secure every electrical connection. The mechanic will also scan the surrounding areas to ensure nothing is overlooked.
They’d reattach the radiator hose and intake if these components were removed earlier to access the alternator.
7. Install the Serpentine Belt
They’ll route the serpentine belt (or alternator belt in case of an older car) around the pulleys using the belt diagram or a reference photo. Next, rotate the tensioner, slip the belt over the alternator pulley, and release the tensioner slowly.
They’ll ensure proper belt alignment and tension.
7. Reconnect the Battery
They’ll install new felt washers on the battery posts and reattach each battery cable to its respective battery terminal. Additionally, the mechanic will apply battery post grease to prevent future acid buildup and corrosion.
8. Test the New Alternator
After installation, they’ll take the vehicle for a short test drive to ensure the car alternator works properly. They’ll monitor the dashboard lights, check if electrical accessories function normally, and listen for any unusual noises from the belt or alternator.
Finally, they’ll use a multimeter to check the voltage at the battery terminals — it should read between 13.5V and 14.7V when the engine is running, indicating proper electrical connection and charging.
While replacing a car’s alternator on your own, it’s important to be aware of common mistakes that can lead to installation issues or alternator failure.
We’ve listed them next.
Common Mistakes to Avoid While Replacing an Alternator
Here are some do’s and don’ts of alternator replacement:
Do’s:
- Use a memory saver to retain your ECU settings.
- Take a picture of the belt routing to avoid any malfunctions.
- Label any wire you disconnect during installation.
Don’ts:
- Avoid over-tightening the belt, which can cause premature wear.
Wondering how much an alternator replacement could set you back?
Keep reading!
How Much Does It Cost to Replace Alternator?
An alternator replacement (including part and labor) 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.
However, the actual price for the replacement alternator will depend on a couple of factors, such as:
- Vehicle make and model: Parts and labor costs for alternator replacement services depend on the type of vehicle you drive. Luxury cars usually undergo costly repairs compared to economy cars.
- Alternator location: Some cars have easy-to-reach alternators, while others, like BMWs, require extra labor, increasing costs.
- Amperage: A higher amperage replacement alternator will cost more due to better materials and power output.
- Wiring complexity: 1-wire alternators (found on older cars) are cheaper than 3-wire versions in modern vehicles.
- New vs rebuilt alternator: New alternators offer more reliability and efficiency with longer warranties but come at a higher cost. A rebuilt alternator, on the other hand, is a more budget-friendly option. However, its performance and lifespan depend on the quality of the rebuild.
- Extra repairs: Issues with other parts of the charging system can add to the total repair cost. For example, a serpentine belt replacement can cost an extra $15 to $80.
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 via the alternator’s stator.
A rectifier, an electrical device inside the alternator, converts this alternating current into direct current, activating your car’s electrical system. By doing so, the alternator, along with the voltage regulator, provides electrical power to accessories like headlights, power steering, power windows, windshield wipers, etc.
2. How Long Does an Alternator Last?
Most alternators have an average lifespan between 80,000 and 150,000 miles. If you follow proper car maintenance, this translates to about seven years of use.
3. Can You Drive with a Bad Alternator?
No, you shouldn’t drive a car with a failing alternator.
A broken 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 electrical power to the starter for cranking the engine, leaving you stranded. This is particularly dangerous if you end up with a dead battery at an intersection or on a busy road.
So it’s better to book an auto service if you start noticing the signs along with an active dashboard light (battery light).
4. Can You Repair a Faulty 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, such as the rotor, can cost almost as much as alternator replacement services. Also, any improper repair can lead to electrical shorts, potentially harming the entire charging system.
Additionally, a new unit will last longer than a rebuilt alternator and usually comes with a warranty.
That said, in some circumstances, it makes more sense to schedule an alternator repair. This includes replacing a worn drive belt, bearings, voltage regulator, diodes, loose or frayed wiring, etc.
5. How to Tell if it’s a Bad Battery or a Bad Alternator
Here’s a surefire way to test if you have an alternator problem or need a battery replacement:
- Connect a running battery to your car’s battery using jumper cables.
- Let it charge for a couple of minutes, then start your vehicle.
- Once it starts, remove the jumper cables. If your engine stalls, you have an alternator issue.
- If it continues to run, you need a battery replacement.
Don’t Let an Alternator Problem Leave You Stranded
Driving with a failing alternator isn’t just risky — it could leave you stuck at the worst time. And while DIY fixes sound tempting, one wrong move can make things worse for your car’s charging system, leading to electrical problems and costly repairs.
That’s why you should let experts at AutoNation Mobile Service handle your car’s alternator.
We bring top-tier auto repair right to your driveway, 7 days a week — no tow trucks, no hassle. Plus, every repair comes with a 12-month, 12,000-mile warranty for peace of mind.
Need an alternator replacement service? Tire repair? Oil change? We’ve got you covered.
Book your service today!