7 Signs of a Failing Alternator | AAMCO Minnesota (2023)

Flickering headlights? Strange noises? Stalling?

These could be signs of a failing alternator.

The alternator is a key component in running the electrical systems in your car. The alternator takes the energy from the crankshaft and turns it into the electricity that is stored in the battery of your car. When your car is running the alternator helps to power the different electrical systems in your car and keep your battery charged.

When your alternator begins to fail it can cause a variety of different electrical problems in your car, and eventually cause a breakdown. Alternators can go bad suddenly, or slowly over time. If your alternator is slowly going bad over time there are some warning signs you can look out for.

So, how do you know if you are having trouble with your alternator?

The Warning Signs of a Failing Alternator

Indicator Lights

Most modern cars have a dashboard warning light to alert you to a problem with your alternator.

7 Signs of a Failing Alternator | AAMCO Minnesota (1)

Typically this light is shaped like a battery, although some warning lights may display GEN (for generator) or ALT (for alternator). The triggering of these warning lights is typically based on how much electricity your car is using and if your alternator’s output drops below a certain level.

Headlight Trouble

Your alternator provides the power to your headlights.7 Signs of a Failing Alternator | AAMCO Minnesota (2)

One of the most common symptoms of a failing alternator is flickering, pulsating, or dimmed headlights. If your alternator is beginning to fail it won’t be able to power your headlights effectively.

Other Electrical Problems

The alternator is responsible for providing power to your car’s different electronics.7 Signs of a Failing Alternator | AAMCO Minnesota (3)

Things like power windows and power seats might start operating at a slower speed than normal or stop working altogether. A dying alternator may also cause your car’s radio and internal lighting to stop working.


Smell burning rubber?

Your alternator works with a series of belts within your car. If these belts are not able to move in their intended ways, they will generate excess friction causing the belt to heat up. This can cause a burning rubber type smell.

7 Signs of a Failing Alternator | AAMCO Minnesota (4)

Smellelectrical burning?

Smelling what smells like an electrical fire could indicate that a belt is slipping and may need to be tightened. In the event that tightening the belt does not resolve the smell or increase your alternator output then it is time to visit a mechanic.

Your local AAMCO Minnesota location can diagnose and repair your electrical system, including your alternator.

Dead Battery

The alternator is responsible for recharging your car’s battery.7 Signs of a Failing Alternator | AAMCO Minnesota (5)

Car batteries can (and do) fail on their own. However, a bad alternator can cause your car battery to drain and not be recharged. If you find yourself jumpstarting your car frequently or your batterydies, be sure to have your alternator checked.

Related: Signs Your Battery Needs to Be Replaced

Stalling or Difficulty Starting

Your car requires this electric spark to start.7 Signs of a Failing Alternator | AAMCO Minnesota (6)

The alternator in your car provides power to the spark plugs that ignite the gas in your engine. If your alternator is beginning to go bad there might not be enough power in your spark plugs to start your car or keep your car running. If you find yourself stalling for seemingly no reason, it could indicate troubles with your alternator.

Related: Reasons Your Car Won’t Start


Strange noises coming from your car can indicate a variety of problems.

Hearing strange noises coming from your engine in conjunction with some of the other symptoms listed could indicate a problem with your alternator. Listen for whining, grinding and rattling sounds as these could all indicate a failing alternator.

What to Do If Your Alternator is Failing

Suspect that your alternator is failing or has failed?

AAMCO Minnesota has top quality mechanics and equipment to diagnose and repair any problems to your cars electrical system. Including:

  • Alternator
  • Drive Belt
  • Voltage Regulator
  • Starter
  • Ignition Switch
  • Neutral Safety Switch
  • Battery Cables & Terminals

Schedule an appointment with your local AAMCO Minnesota location to have your alternator or other electrical systems checked for performance and safety today.


How do I tell the difference between a bad alternator and a bad battery? ›

If the engine starts but dies immediately, your alternator probably isn't keeping your battery charged. If a jump starts and keeps your car running, but the car can't start again off of its own power, a dead battery is probably your answer.

What happens when your alternator goes out while driving? ›

What happens when alternator stops working while driving? The car tends to slowly lose power if the alternator has gone bad while the car is being driven. You'll notice the headlights start to dim shortly before the car loses power and dies.

What usually fails in an alternator? ›

One of the most common problems you're likely to experience with an alternator is a failure in the bearings. There are needle bearings in the alternator that allow the rotor to freely spin inside the housing, and those bearings can break down over time as a result of exposure to heat and dirt.

Do alternators fail suddenly? ›

Alternators can go bad suddenly, or slowly over time. If your alternator is slowly going bad over time there are some warning signs you can look out for.

How can I test my alternator without removing it? ›

“With the car running, you can turn on all the heavy loads; turn on the heater blower motor, turn the lights on, etc.,” he tells us. “Then check the voltage at the battery terminals. That'll give you a general idea of the health of the alternator.”

How can I tell if my alternator is bad without tools? ›

Test the alternator by starting the engine and disconnecting the battery terminal. The engine should continue to run without stalling. If it does stall, then the alternator is not functioning properly.

How does a car act with a bad alternator? ›

Signs of a Bad Alternator

Some of the things to look for are no-starting and trouble starting, dimming lights and problems with stereo system output. If your car starts but stalls when you're underway, your battery is probably not being recharged due to a faulty alternator.

What does alternator problems sound like? ›

If you're hearing a grinding sound in your car, this could indicate that the alternator is going bad. The grinding sound may be caused by a worn-out bearing. Your car can also make a whining sound when the voltage regulator is sending signals to the alternator to charge more than is necessary.

Will a bad alternator throw a code? ›

If you have a “Check Engine" light on, connect a code reader to the diagnostic port. If you find code P0562, you very likely have a failing alternator (note that codes may vary by vehicle make/model/year). Get it checked out before it fails entirely.

How can you tell if you need a new battery or alternator? ›

If the [battery's] voltage is low, replace with a new battery or charge the battery to the recommended 14.2 to 14.7 volts,” he says. “Then try to run the vehicle and see if the voltage after is outside of that range. If it is, that's a sign of a bad alternator.”

How do you test an alternator vs a battery? ›

However, a very simple way to check if the alternator is working is to run the car and disconnect the positive terminal of the battery. If the vehicle stops running, then you probably have a bad alternator. You can also examine your interior and dashboard lights.

How do you check a car battery or alternator? ›

A simple test to check the working of the alternator is by running your car; and then unplugging the positive connection of the battery. If the car stops, then you most likely have a problem with the alternator. Another simple test is to check your interior lights.

Can you jumpstart a car with a bad alternator? ›

Can you jumpstart a car with a bad alternator? It is possible in some cases to jumpstart a vehicle that has a faulty alternator, as long as the battery has enough of a charge to keep running. However, the alternator should be replaced as soon as possible.


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