A faulty alternator can produce several different sounds, and the specific noise you hear may depend on the nature and severity of the problem. Here are some common sounds associated with a faulty alternator:

1. Whining or Grinding Noise: A whining or grinding noise is often a sign of a worn-out or damaged alternator bearing. When the bearing inside the alternator starts to wear down, it can produce a high-pitched whining or grinding sound. This noise may become more pronounced as the alternator spins faster with increased engine RPMs.
2. Squealing or Screeching Noise: A squealing or screeching noise typically occurs when the alternator drive belt or serpentine belt is loose, worn, or misaligned. This sound is more noticeable when you accelerate or turn the steering wheel, putting additional strain on the belt.
3. Clicking or Ticking Noise: In some cases, a failing alternator can produce a clicking or ticking noise. This noise may be caused by damaged or worn-out internal components within the alternator, such as brushes or diodes.
4. Electrical Noise: Faulty alternators can also generate electrical noise, which may manifest as a buzzing or crackling sound. This can be a sign of issues with the alternator’s electrical components, such as rectifiers or voltage regulators.
5. Dimming Lights: While not a sound, a noticeable dimming of your vehicle’s headlights and interior lights can also indicate alternator problems. When the alternator isn’t generating enough power, your vehicle’s electrical system may draw power from the battery, causing lights to dim.

If you suspect your alternator is faulty based on these sounds or other symptoms like warning lights on the dashboard (e.g., battery light), it’s essential to address the issue promptly. A failing alternator can lead to a dead battery and leave you stranded if not repaired or replaced. It’s advisable to have a professional mechanic inspect and diagnose the problem to determine the exact cause of the noise and whether the alternator needs repair or replacement.

A bad alternator typically doesn’t produce specific sounds when you’re trying to start the engine, as the alternator is primarily responsible for charging the battery and providing electrical power to your vehicle while it’s running. However, when you attempt to start your vehicle with a bad alternator, you may experience the following symptoms:

1. Slow or Weak Cranking: When you turn the key to start the engine, a bad alternator can’t supply enough electrical power to the starter motor. As a result, the starter motor may turn slowly or struggle to crank the engine. This can make the engine sound like it’s struggling or not turning over at its usual speed.
2. Clicking Sound: If the alternator is severely damaged or has failed completely, it may not provide any electrical power to the starter motor. In this case, you may hear a rapid clicking sound when you try to start the engine. This clicking is typically the sound of the starter solenoid engaging repeatedly due to insufficient power.
3. Dimming Lights: As the alternator is responsible for providing power to your vehicle’s electrical system, including the lights, you may notice the lights dimming significantly when you attempt to start the engine. This dimming can be a sign that the alternator isn’t supplying enough electricity.

It’s essential to note that while these symptoms can be associated with a bad alternator, they can also be caused by other issues, such as a weak or discharged battery, corroded battery terminals, or a faulty starter motor. To accurately diagnose the problem and determine if the alternator is the issue, it’s best to have your vehicle inspected by a qualified mechanic. They can perform electrical system tests and assess the condition of the alternator and battery to identify the root cause of the starting problems.

A car with a bad alternator can continue running for a short period, but it’s not sustainable. Once the alternator fails, the car will rely solely on the battery to power the electrical systems.

Here’s how long it might last:

1. Battery life: If the alternator is bad, the battery will only last as long as its stored charge. Depending on the battery’s health and how much power is being used, this could be anywhere from 30 minutes to a couple of hours.
2. Electrical load: The more electrical components running (like headlights, air conditioning, radio, etc.), the faster the battery will drain. If the car is just idling with minimal electrical load, it could last longer.
3. Warning signs: The car may start to show signs of electrical issues as the battery drains, like dimming lights, flickering dashboard lights, or loss of power to accessories. If the battery charge runs out completely, the car will eventually stall.

To avoid being stranded, it’s best to get the alternator fixed as soon as possible after noticing issues like dim lights or electrical malfunctions.

The lifespan of an alternator can vary depending on several factors, including the make and model of the vehicle, driving conditions, maintenance practices, and the quality of the alternator itself. On average, a well-maintained alternator can last anywhere from 100,000 to 150,000 miles (160,000 to 240,000 kilometers) or more. However, some alternators can fail sooner, while others may last significantly longer.

Here are some factors that can influence the lifespan of an alternator:

1. Vehicle Make and Model: Different vehicles have different alternator designs and quality standards. Some vehicles may have alternators that are more prone to issues or failures, while others may have more reliable alternators.
2. Driving Conditions: Harsh driving conditions, such as frequent short trips, stop-and-go traffic, or extreme temperatures, can put extra stress on the alternator and other vehicle components. This can lead to a shorter lifespan.
3. Maintenance: Regular maintenance, including checking and tightening the alternator belt, inspecting the electrical system, and keeping the serpentine or drive belt in good condition, can help extend the life of the alternator.
4. Electrical Load: Vehicles with high electrical demands due to aftermarket accessories or heavy use of electrical components may put more strain on the alternator, potentially shortening its lifespan.
5. Quality of the Alternator: The quality and brand of the alternator can also play a significant role. Higher-quality alternators may be more durable and have longer lifespans than cheaper alternatives.
6. Manufacturing Defects: In some cases, alternators may fail prematurely due to manufacturing defects or other unforeseen issues.

It’s important to pay attention to signs of alternator problems, such as dimming lights, warning lights on the dashboard (e.g., battery light), strange noises, or difficulty starting the vehicle. Promptly addressing these issues through diagnosis and repair or replacement can help prevent more significant problems and extend the alternator’s lifespan.

Regular maintenance and periodic inspections by a qualified mechanic can also help identify potential alternator issues before they become serious, potentially saving you from unexpected breakdowns.