7 Symptoms Of A Failing Alternator

Here are 7 telling signs that your car may need alternator repair or replacement:

1. Dead Battery

The alternator is largely responsible for charging the vehicle battery while it’s running. So, if the battery isn’t charging or suddenly dies, it could be because of a malfunctioning alternator.

In this case, recharging the battery won’t be enough to resolve the issue. You may have to replace the alternator or dead battery.

2. Hard Starting or Stalling Engine

If the alternator isn’t charging the battery, you may experience trouble starting the car — also called a hard start. You could even experience a stalling engine when the car is running, which would be pretty bad if you happened to be driving.

As such, it’s helpful to seek auto repair before the battery dies. Of course, hard starts could also be due to a malfunctioning starter. 

3. Dim Or Flickering Lights

You may experience dim or flickering lights if a failed alternator isn’t sending enough power to the electrical components. Alternatively, you could get extremely bright lights if the alternator sends too much electrical power. 

This is an obvious sign of battery or alternator trouble, and these issues may worsen as the alternator wears down further.

4. Low Electrical Output

Apart from dim lights, sluggish accessories (like slow power windows or failing air conditioning) are another sign that you may need an alternator or car battery replacement.

A failing alternator will provide a diminished power supply to these electrical accessories and reduce their functionality. And as the alternator’s condition worsens, you may even notice failing electrical gauges, like the speedometer.

At this point, it’s advisable to repair the alternator as soon as possible.

5. Squealing Or Whining Noise

A bad alternator may sometimes cause a squealing or whining noise when the car is running. 

Why does this happen?

The noise can come from a misaligned alternator pulley rubbing against the drive belt (serpentine belt or v-belt). It could also occur because the pulley’s bearings are worn out.

Regardless, both a misaligned alternator pulley and worn-out bearings can lead to a malfunctioning alternator. 

Tip: Inform your mechanic about the sounds you hear from the engine bay. A whining sound (usually a misaligned pulley) indicates a different alternator problem from a rattling sound (commonly due to bad bearings).

6. Burning Smell

A burning or hot rubber smell can indicate a drive belt or alternator pulley problem. Additionally, rubbing parts or a vehicle’s electrical system issues can involve a fire. So, it’s important to have a bad alternator checked immediately.

7. Lit Warning Lights

Your car may try to warn you about alternator failure through one of these dashboard warning lights:

• Battery light
• Check engine light
• Charging system light

These warning lights could indicate that the alternator isn’t charging the battery or providing enough electrical energy to the electronic control unit. Even if it’s not the alternator, you may need to seek out an engine repair service.

Note: An alternator repair or replacement is pretty important. That’s why it’s beneficial to seek an auto repair service as soon as you notice any signs of a bad alternator.

How Urgent Is An Alternator Replacement?

If the alternator fails, the battery won’t charge and the car won’t run as it should.

Issues with stalling and starting may leave you running late. Additionally, a faulty alternator can damage certain electrical components by overcharging or undercharging them.

So, a faulty alternator is best replaced at the earliest. In fact, it can even be beneficial to have an old alternator checked regularly, like when availing tire repair or oil change services.

How Much Does An Alternator Replacement Cost?

The average alternator repair cost is between $375 to $1,100. However, these numbers can vary based on the parts needing repair or replacement, car model, and labor cost.

The estimated cost for parts (including a replacement belt) can range from $290 to $600. And labor can cost between $85 to $800 depending on where you get the repair service.

Why?

Vehicles with greater electrical needs, like ambulances or newer car models, may use a high-output alternator. These alternators are more expensive than typical stock alternators. 

For example, an alternator replacement for a Mercedes Benz E350 can cost between $907 to $942, with the parts alone costing $771.

However, if you can’t afford a new alternator, you could always ask your local mechanic for a remanufactured or rebuilt car alternator. Make sure there’s a warranty to cover any potential problems.

4 Alternator Replacement FAQs

Here are answers to four common questions on alternator replacement:

1. What Is An Alternator?

An alternator is a component of the car charging system, connected to the engine by a drive belt. It consists of several crucial parts, including a rectifier and voltage regulator, that help ensure your vehicle’s electrical components and cooling system are powered.

It’s responsible for:

• Recharging the car battery by converting mechanical energy into electrical energy. Alternating current generated by the alternator is output as direct current through the rectifier diodes.
• Supplying power to the cooling system and electrical accessories, like the headlights, power windows, and more.

So, your vehicle’s performance is dependent on how well the car alternator works.

2. Can I Drive With Alternator Problems?

Yes, you can drive your vehicle while experiencing alternator failure — at least for a while.

But it’ll only last for so long before the battery dies. At this point, you may need to jumpstart the vehicle or rely on a towing service to get it to a repair shop.

However, if a bad alternator causes electrical system issues while the vehicle is running, it can be helpful to resolve the alternator problem before you require additional engine repair.

3. How Often Do I Need To Replace The Alternator?

Generally, an alternator can last for around 150,000 miles or seven to eight years before needing replacement.

However, alternator failure is pretty common, and an alternator’s lifespan can vary based on aspects like:

• Driving conditions, like weather and traffic
• Custom power accessories and heavy electrical system load
• Vehicle and engine type
• Fluid leaks onto the alternator

So, it’s good to get your alternator checked whenever you go for any automotive service, like getting your car battery tested or even tire services. 

4. How Do I Replace An Alternator?

The alternator powers critical car components. So, instead of attempting a DIY replacement, it’s best to leave the job to professionals (like ASE certified technicians).

Here’s how a mechanic at your dealership will replace a failed alternator:

• Disconnect the negative battery cable.

• Disconnect the wires connected to the back of the alternator. 

• Remove the alternator belt from the pulley by loosening the belt tensioner.

• Once the belt is off, unfasten the bolts connecting the alternator to the bracket.
• Remove the old alternator from the bracket.

• Compare the new alternator with the old alternator and check whether everything matches, including the mounting bolt holes.
• Install the new alternator and tighten the mounting bolts with a ratchet.
• Slip the alternator belt back in position by using the tensioner arm.

• Review the installation and test the alternator output using a multimeter. 

Tip: Ensure you fully charge the battery with a charger after the installation. Using the new alternator to charge a low volt battery can damage the alternator.