How do you know if your alternator is bad?

Asked By: Mazen Ricca | Last Updated: 27th February, 2020
Category: automotive auto parts
4.1/5 (41 Views . 37 Votes)
Six Alternator Warning Signs:
  1. Dim lights. The alternator is part of the electrical system of your vehicle.
  2. Warning light. Most modern cars have a dashboard warning light that alerts you when the alternator is on the fritz.
  3. Weak or dead battery.
  4. Weird smells.
  5. Odd sounds.
  6. Visual cues.

Click to see full answer


Likewise, what are the symptoms of a bad alternator?

6 Symptoms of a Failing Alternator

  • The indicator light.
  • Headlights are dim or flickering.
  • Other electrical failures.
  • Strange noises.
  • Car stalls or has difficulty starting.
  • Battery dies.

Secondly, how do you check if your alternator is working? Alternator test with a voltmeter If it's in the range, it's good. Connect the meter leads to the battery terminals and look for 13.8 to 15.3 volts (engine running, lights and accessories off). That means the alternator is pumping out the juice.

Also Know, how do you know if its battery or alternator?

Signs of a dead battery The battery should be giving a charge, even while the vehicle is off. If you can't get it to restart, this is a sign the alternator is doing its job of keeping the battery working while the motor is running, but the battery isn't retaining the charge when the alternator has stopped.

How much does it cost to replace an alternator?

Waits says the average price to replace an alternator with a remanufactured one is $400, while Gunning adds that a remanufactured alternator on a typical, domestic car, costs about $300 to $500, including parts and labor. The price of a new alternator can run from $500 to $1,000.

37 Related Question Answers Found

What does a failing alternator sound like?

An alternator has a lot of moving parts that spin when it's working correctly. 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.

What can burn out an alternator?

This could cause the battery to run down over time. Diode failures may also allow AC current to leak into the electrical system. A leaky diode also can allow current to drain out of the battery through the alternator when the vehicle is not being driven. A faulty voltage regulator can also cause charging problems.

What happens when an alternator goes out?

The alternator keeps things electrically charged and going. If it fails, you're stuck – and it can go bad slowly or suddenly. When the car is running, the charging system (alternator, voltage regulator) should recharge the battery and provide sufficient electrical power to the vehicle. The battery serves as a backup.

How do I know if its my starter or alternator?

Signs the Alternator has Failed:
You notice that your headlights or your dash lights flicker or get extra dim or bright. Or that your gauges are behaving strangely. If you jump start your car and it will start, but the engine dies right after the jump then it is most likely the alternator.

Can a bad alternator kill a battery?

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 battery dies, be sure to have your alternator checked.

Can a bad alternator destroy a new battery?

A) A bad alternator will result in a discharged (dead) battery and cause a vehicle to not start or run.

How does a car's alternator work?

An alternator works together with the battery to supply power for the electrical components of the vehicle. The output of an alternator is direct current (DC). When the alternator pulley is rotated, alternating current (AC) passes through a magnetic field and an electrical current is generated.

How do you test a battery?

Follow these steps to test your battery:
  1. Before you begin testing, make sure the ignition key and all of your vehicle's lights are off.
  2. Connect the red or positive voltmeter test lead to your battery's positive terminal.
  3. Then, connect the black or negative voltmeter test lead to your battery's negative terminal.

When the battery light comes on what does that mean?


A simple circuit looks at the voltage that the alternator is producing, and turns the battery light on if it is low. The battery light indicates a battery charging problem. If the battery light comes on and stays on while you are driving, the most common cause is a broken alternator belt.

What are signs of a bad battery?

Watch for these five telltale signs of a bad battery so you aren't caught out in the cold!
  • Dim headlights.
  • Clicking sound when you turn the key.
  • Slow crank.
  • Needing to press on the gas pedal to start.
  • Backfiring.

When your car won't start but all the lights come on?

Broken or Damaged Ignition
If your headlights can turn on, but your car won't crank, that means that your battery is charged, but either the starter or ignition is the problem. If the starter or ignition is the problem, a starter engine can be jumped by using a charged battery.

Will AutoZone test your alternator?

AutoZone will test your car's parts for free. We can test your car's battery*, alternator*, starter* and voltage regulator while they're still on your car. We can also give your car a complete starting and charging systems test. You can also take your alternator, starter or battery into our store and we'll test it.

How do you clean an alternator without removing it?

How to clean your alternators.
  1. Do not use petroleum based engine degreasers to clean the alternator.
  2. Do not use compressed air or a pressure washer to clean the alternator.
  3. Do not spray a cleaning agent or degreaser directly into any air inlet openings on the alternator.

How much is an alternator tester?


In Stock. I work at a Lexus dealership. We have a shop supplied MidTronics battery tester that costs over $1,000.

Top Selected Products and Reviews.
List Price: $199.99
You Save: $140.00 (70%)

How do you test a smart alternator?

The usual way of testing these units is to apply a multimeter across the battery terminals to check that the voltage does not dip above, or below, 13 volts. This should be checked with and without the headlights, heated rear windscreen and interior fan switched on – the reading should remain fairly consistent.

Where is the alternator located?

The alternator is located at the drivebelt end of the engine (it is driven by the belt). Most often the alternator is high on the engine and accessible from under the hood.