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Top 5 Warning Signs of a Failing Alternator

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What does an alternator do, anyway? You hear about it, but you aren’t quite sure.

Its primary job? To keep your battery charged while you drive and to power your electrical system. Every time you turn on your headlights, use your infotainment system, or crank the heat, your alternator is hard at work converting mechanical energy into electrical current.

When it fails, the results can be serious. And that can be bad news if you’re out on Colorado roads. Imagine a breakdown on a cold winter morning, or on one of our remote roads. That can be inconvenient or even dangerous.

Yep, your alternator is important. So let’s break down the top five signs your alternator might be failing, and why it pays to act fast.

Your Battery Keeps Dying

This is one of the most common—and misleading—symptoms of a failing alternator.

At first glance, it may seem like your battery is the problem. You jumpstart your car and it runs fine … for a while. But if your battery keeps losing charge, the real issue might be your alternator failing to recharge it as you drive.

Here’s what you should look for:

  • Needing frequent jumpstarts
  • A new battery that dies quickly
  • Dimming lights or sluggish electrical systems even when the engine is on

All of these are signs it might be your alternator. A dead battery is annoying, but if the alternator is to blame, you could be minutes from being stranded with a car that won’t start again.

Top 5 Warning Signs of a Failing Alternator

Dim or Flickering Headlights and Interior Lights

Ever notice your headlights seem unusually dim when idling at a stoplight, then brighten as you accelerate? That’s a telltale sign your alternator is struggling to provide a consistent current.

Your alternator powers all of your vehicle’s lighting while the engine is running. When it starts to fail, it might still generate some power, but it won’t be enough to handle everything.

You may notice:

  • Dim dashboard lights
  • Headlights that flicker or fade in and out
  • Cabin lights that pulse with engine RPM

We get it, it’s sometimes difficult to tell how bright your lights are with the big city lights. But driving through dark mountain roads or snowy evenings without consistent headlights is more than just frustrating, it’s dangerous. Check it from time to time, especially if you change up where and how you drive. If your lighting is acting up, get your alternator checked.

Strange Noises From Under the Hood

A failing alternator can sometimes make itself known through sound.

The alternator has a rotor that spins rapidly inside a housing, driven by a belt connected to your engine. If the bearings inside begin to fail or the belt becomes misaligned or loose, you may start to hear some unwelcome sounds.

You’ll notice it if you hear:

  • A whining or grinding sound that increases with acceleration
  • Chirping or squealing from a worn or slipping serpentine belt

These noises may point to worn-out internal parts or belt issues that can cause your alternator to stop charging altogether. Catching it early can save you from being stranded or facing more expensive repairs.

Warning Lights on Your Dashboard

Ever ignored the little lights on your dashboard? We get that not all of them indicate “stop your car now” situations. That little battery-shaped warning light on your dash doesn’t just mean your battery is low; it can also indicate a charging issue, including a failing alternator.

In many vehicles, when the alternator fails or voltage drops too low, the electrical system will trigger a warning.

Look for dashboard lights such as:

  • Battery light
  • Check engine light
  • ABS or other system errors related to voltage fluctuation

Sometimes these warnings come and go. Don’t ignore them. They’re your vehicle’s way of telling you something is wrong. More importantly, inconsistent voltage can cause your car to run erratically, affecting engine performance, power steering, and other systems. Don’t wait for it to get worse.

Electrical Failures Across the Vehicle

Your car’s alternator powers more than you might realize. It includes your:

  • Power windows
  • Heated seats
  • Stereo system
  • Windshield wipers
  • GPS
  • Phone charger
  • Dashboard displays

If you’re noticing that multiple systems are acting strange, glitching, or failing entirely, even though your battery is new, your alternator may not be keeping up.

Watch for:

  • Random electrical malfunctions
  • Glitches in your infotainment or climate control
  • Failing power seats, mirrors, or locks

If it runs on electricity and it’s failing, your alternator might be the root cause.

Bonus: Colorado Drivers, Take Extra Precautions

Colorado weather doesn’t mess around. And Denver drivers face a few unique alternator stressors:

  • Extreme Temperature Swings: From freezing mornings to hot summer afternoons, temperature shifts can wear down alternator components faster.
  • Mountain Drives: Steep climbs and descents increase engine strain and make electrical systems work harder, especially headlights, brakes, and onboard computers.
  • Winter Load: Heaters, defrosters, and heated seats increase electrical demand, revealing alternator problems faster.

That’s why regular checkups matter even more here in Denver, especially if you take advantage of all Colorado has to offer. Catching a failing alternator early can keep you off the side of I-70 or stuck in a snowy parking lot.

What To Do If You Suspect a Failing Alternator

If you’ve noticed one or more of these signs, don’t wait until your car leaves you stranded. Schedule an inspection.

At our shop, we’ll:

  • Test your alternator output with specialized equipment
  • Check your battery health and charging system
  • Inspect belts and connections for wear or corrosion
  • Recommend the best fix based on your vehicle and driving habits

Many alternator issues start small, and are simple to fix. Left unchecked, they can lead to bigger, more expensive problems like a dead battery, faulty sensors, or computer errors.

A healthy alternator is essential for a safe and reliable car. It powers the systems you rely on every day.

So when something feels off, don’t brush it off. Your alternator may be trying to tell you it’s on its way out.

Bring your car in for a quick check. We’ll make sure everything’s running smoothly so you can drive with confidence, whether you’re commuting through Denver traffic or heading for the hills.

Diagnosing a Failing Alternator

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How do you know if you have a failing alternator?

Let’s start at the beginning and define what an alternator actually does.

The job of an alternator

Why do the lights stay on in your car? What controls the radio? What gives the starter the ability to start your engine running?

Nope, it’s not the battery. It’s the alternator.

The battery provides a sudden surge of electricity to the motor to start the car. Once this occurs, it’s the alternator that provides the energy to feed the electrical system, and to provide a charge back to the battery.

Think of the alternator as a generator. As the engine runs, the alternator provides electrical power throughout the system to keep everything running. It’s bolted to the engine, and is operated by a serpentine belt.

In most cases, your alternator is a maintenance-free component on your vehicle. You don’t have to add new fluids, or rotate parts out on a regular cycle. For some cars, the alternator can easily last ten, fifteen years or more without creating a problem within the system.

If an alternator does fail, it defaults back to the battery, relying on it for the short term to keep things running. But as the battery charge depletes, the engine will stall.

Diagnosing a Failing AlternatorBecause the alternator is a vital component of your car, it’s important to learn the warning signs and know how a problem will impact the ride. Here are some of the warning signs that may materialize.

Warning light 

Thanks to technology, your dashboard lighting system will warn you of almost any problem your vehicle faces. When a light appears, it’s your job to recognize it and find a solution as quickly as possible. This is the best way to avoid bigger, more costly problems down the road.

On most vehicles, a problem with your alternator will show up as a small battery light. Some will light up “ALT” or “GEN” for alternator or generator. Because people see the battery light, it’s easy to slip into a mild comfort, making plans to have the battery checked at a later date. But in this case, this isn’t why the light turns on.

The battery light covers a whole host of different systems within the car. It also monitors the voltage output of the alternator, and when it goes below a predetermined limit, the light comes on. It will remain lit until action is taken.

Sometimes the light flickers, or comes on when more energy is needed. For example, if you have the windshield wipers on during a rainstorm, and your lights turn on too. In this case, small amounts of energy does not trigger a problem. But when multiple systems are used, it drains the alternator. If the battery light pops on then, it’s the alternator warning you it’s not working at its full potential.

Dim lights

Because the alternator provides power for the electrical accessories in your vehicle, if you notice a problem with any of them, it could be a sign of a weak alternator.

One of the most used accessories is your lights, both inside your car and the headlamps on the outside. If you find yourself thinking it’s darker inside your car when you flip on the lights, or you see very little difference between the standard lights and the brights, it could be a sign your alternator has an issue.

Likewise, if you notice them flickering, it could also be a sign the alternator isn’t generating enough power to keep the accessories fully charged. To be able to help a mechanic out and pinpoint the problem, watch for patterns. Can you determine when the problem happens the most? That will help narrow down where the trigger points lie.

Dead battery

Batteries are only designed to last several years. Keep that in mind, especially if you start noticing problems with the power in your car.

Diagnosing a problem with the alternator instead of a dead battery is easy. Use jumper cables to jumpstart your car. Remove them as quickly as possible. If the battery cranks over, and the alternator fails to charge, the car will die shortly after removal.

Use caution when jumping to conclusions about what’s wrong with your car, especially if it’s an older vehicle. A good mechanic can help you pinpoint the problem, and give you viable options for different ways to handle every situation.

Difficulty starting

Sometimes you turn the key expecting it to start and the car won’t engage. This can be a symptom of a problem with the alternator. However, because so much is attached to the electrical system, and controlled by the connection between the battery and the alternator, it’s important to evaluate all pieces before making a final call.

Strange smell

If the alternator isn’t working correctly, it might be producing too much heat somewhere in the system.

Have you ever smelled burning from an electrical fire? That can occur if your alternator overheats.

Have you smelled burning rubber? It might smell a little like that too. The belt that keeps the alternator moving, doing its job, is made out of rubber. So if the system overheats, it might produce the smell of burning rubber.

Strange sounds

When certain parts wear down, they start impacting other parts near them. And as this happens, it can create strange sounds. A failing alternator is often described as having a “whining” sound.

The alternator is driven by a serpentine belt, which works in conjunction with a crankshaft pulley to produce power. This belt spins faster than the pulley system, and if it’s not supported properly on the shaft it sits on, it can create friction resulting in a whining sound.

Of course, if you ignore the problem and the alternator continues to wear, it can cause further damage. The whine can move to other sounds, possibly clanking or rattles if belts brake, bolts fail, and parts disappear.

Your course of action matters

Bringing your vehicle in may not be on your list of to do’s. But the sooner you bring it in, the quicker action we can take when we figure out what’s wrong.

A failing alternator can require less repair work if you catch the problem early.

If you have a question about anything not working correctly on your vehicle, bring it in. We’ll diagnose it and give you your options, and help you make the best decision for your situation.

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