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What Does an Alternator Do?

What Does an Alternator Do?Car batteries and alternators; you can’t have one without the other! Car batteries rely on the alternator to keep them powered up as you drive.

In short, the alternator supplies electricity to the vehicle’s computer and to your battery. Once your vehicle’s battery is used to start your vehicle the power expended to help start the engine is depleted and needs to be replenished somehow. The replenisher, more commonly known as the alternator, is tasked with creating and continuing to supply power to the battery and other electrical components within the vehicle.

The Charging System

The alternator is usually bolted to the front of the engine and is driven by the crankshaft aided by the serpentine belt. Though it plays a vital role in the charging system, it is just one of a few components. The charging system, in addition to the alternator, includes the battery and a voltage regulator.

What does a regulator do in an alternator?

It regulates power created by the alternator to the battery and other accessories. The alternator’s task is to convert mechanical energy to electrical energy with an alternating current (AC). An alternator has an outer metal casing that houses the stator and rotor, diodes, voltage regulator, and cooling fan.

  • Stator and Rotor are magnets that rotate to create the alternating current for transforming energy into electricity.
  • Diodes transform alternating current into the direct current to charge the battery. The diodes also ensure that the current only travels one way–to the battery and not back to the alternator.
  • Voltage Regulator regulates the amount of electricity produced by the alternator and helps to prevent power surges.
  • Cooling Fan can be located on either the inside or the outside of the alternator and is meant to protect all internal components from getting too hot. Heat that is generated from the creation of energy is dissipated by the movement of air.

How long does an alternator last?

A good alternator can last up to 100,000 miles in reasonable conditions. Here in Arizona, due to our severe climate, the lifespan may be a bit shorter, however. There are symptoms that may clue you in if the alternator is beginning to fail. You may notice some minor unusual behavior such as:

  • Flickering headlights
  • Dim headlights
  • Difficulty starting the car

Other times, there may be more obvious symptoms that the alternator is struggling, indicating that the electrical system will need to be tested. These symptoms include:

  • Unpleasant Odor – A smell, such as burning rubber, is indicative that rubber belts are failing to rotate creating intense friction. As a result of the increase in friction, heat builds up and emits an unpleasant smell.
  • Weak or Dead Battery – A bad alternator can drain a perfectly good battery. While the alternator’s main task is to direct power to the battery, it is unable to restore power to an already weak or dead battery. So how can you tell if you have just a dead battery or the alternator is causing the battery to die? This “chicken or the egg” situation can be tested to determine which component is at fault. Using jumper cables, jump start your vehicle and remove cables instantly. If the vehicle immediately stalls, it indicates the alternator is likely at fault. Conversely, if the vehicle continues to run after several minutes, this indicates the battery is the problem.
  • Weak Electrical Components – In addition to the possibility of a dim dashboard and headlights, you may also recognize difficulties with power windows and seats, difficulty operating the radio, slow windshield wipers, or other lagging electrically operated components.
  • Dashboard Warning Lights – Your vehicle is loaded with sensors all over the vehicle that communicate with the internal computer. When certain sensors communicate an abnormality in the related system, the internal computer triggers a light to come on the dashboard. In cases where the alternator is losing power, you may notice the letters ALT or GEN, the check engine light, or a battery shaped symbol.
  • Strange Noises – Bearings, the stator and rotor, and other components that are spinning inside the alternator to create the energy can begin to fail and produce whining or grinding sounds.

Get an Expert Opinion

It’s perfectly acceptable to test your charging system using your jumper cables to determine whether the alternator or battery are at fault or to tighten the tensioner to prevent the belt from slipping, however, it’s best to leave the repairs to a qualified technician. Repairing an already failed alternator or replacing the old one with a new one may prove difficult or can pose a danger to the amateur DIYer.

New or Rebuilt?

Alternators and batteries are essential to powering your vehicle. Alternators in particular are fairly complicated by design and replacements can be expensive. When it comes to choosing to replace your vehicle’s alternator, you have the option to purchase a rebuilt alternator or a brand new OEM version. A rebuilt alternator is basically a refurbished model that had previously defective parts replaced or repaired. Alternately, your failed alternator may be removed and sent to a specialty shop for repairs and then reinstalled. While both options are acceptable and more cost effective, you’re risking reliability. Opting for a new alternator may be a better choice as it may last longer than the others.