Your Trusted Auto Repair Shop for 40+ Years
Shop Talk Logo

What Does A Car’s Alternator Do?

what does an alternator doMost every driver knows the most basic yet major components of their vehicle. Components such as the engine, transmission, battery, and alternator. We know that engines create the propulsion to begin moving, the transmission keeps the vehicle moving, and the battery helps start the engine, but what does the alternator do?  The alternator in your car is the boss when it comes to generating power. Sure, your battery is the one that initially gets your car started, but once that cycle is complete, its job is mostly done until the next time you need to start your engine. There’s a lot of power needed to start a car and keep it running. That’s where the alternator comes in. The alternator creates and continues to supply power to the battery as well as supply power to electrical components in the vehicle. 

What Is an Alternator?

The alternator is one of the three major components needed to provide electrical power in your vehicle. In short, the charging system, made up of the alternator, battery, and voltage regulator create, supply, and regulate power. The alternator creates electrical energy from mechanical energy with an alternating current (AC). The alternator is most often found bolted near the front of the engine and is driven by the crankshaft with the use of a serpentine belt. The alternator itself contains smaller components to aid in generating power including:

Stator and Rotor: Magnets inside of the alternator that spin to create the alternating current to convert energy into electricity.

Diodes: Transforms the alternating current into a direct current for charging the battery and allowing for the current to travel in just one direction; from the alternator to the battery.

Voltage Regulator: Prevents power surges by ensuring voltage stays in the appropriate range. 

Cooling Fan: Located on the inside or outside of the alternator to protect internal components from overheating by dissipating heat that is generated from the formation of energy.

How Long Does an Alternator Last?

Alternators do not demand much attention unless of course, they are in failure. Most alternators will last anywhere between 7-10 years in ideal conditions. However, there are some ways to tell if your alternator is bad. Flickering headlights, dim lights on the dashboard, and trouble starting your vehicle are just some minor clues that your alternator is struggling. If your vehicle is showing any of these symptoms along with others listed below, it may be time to have your electrical system tested:

Weak Battery

Though the alternator’s duty is to send power to the battery, it cannot revive an already weak or dead battery. If you’re not sure whether the battery or the alternator is the cause of your electrical failure, you can test the vehicle yourself with the use of jumper cables. Jumpstart your car and remove the cables immediately. If the alternator is unable to charge the system and the car immediately dies, the alternator is at fault. If the vehicle continues to run after several minutes, the battery is likely your culprit. 

Battery Light On

Your vehicle is equipped with many sensors that communicate to your vehicle’s internal computer and any notifications that need to be communicated to the driver, are displayed on the vehicle’s dashboard, including electrical issues. You may notice a battery shaped icon, the letters ALT or GEN when the alternator’s power begins to fade. 

Grinding or Whining Noise

The stator and rotor, bearings, and other components are spinning within the alternator to create the energy, however, if any of these components begin to fail, it may produce an unpleasant whining or grinding sound.

Lagging Electrical Components

This is perhaps the most obvious sign of trouble. A dim dashboard or headlights and lagging accessories such as slow working windshield wipers, power windows, seats, or a radio cutting in and out are signs that the alternator is struggling to create or maintain any power. 

Foul Smell

A burning rubber stench can be produced by belts that are failing to turn and due to the increase in friction, the belt heats up producing the odor. A belt slipping on the alternator’s pulley will smell more similar to an electrical fire, indicating the belt needs to be tightened. If the belt has already been adjusted, a technician will need to test the alternator’s function.

Diagnosing and Replacing the Alternator

If you notice any of the unusual behavior as described above, take a quick look under the hood with a visual inspection of the alternator’s belt. Look for any signs of slipping such as a glassiness or a burnt appearance. Belts that are loose can slip on the pulleys which produce friction for the metal to rubber contact which in turn heats up the rubber causing the belt to wear out faster. To resolve the issue, tighten the tensioner. Take care not to overtighten it though, or you risk damaging delicate components inside the alternator. 

Alternators are essential components to the vehicle and somewhat complicated in their design. Replacing the alternator in your vehicle can be pricey. Luckily, you have options when it comes to alternator replacement. You can purchase a rebuilt alternator or a new OEM (Original Manufacturer Equipment) alternator. A rebuilt alternator is essentially a used alternator that has had defective parts removed and repaired or replaced. In some cases, your original alternator will be removed from your vehicle and sent to a specialty shop for repair. While a brand new alternator may be more costly, it’s likely more reliable. Purchasing a rebuilt alternator is a risk; though the internal components have been removed and replaced, there’s a possibility it may not be in a like-new condition.