Posted under Car Engine

You may think the battery is the source of automotive energy, but that’s only half true. Your battery is essential for cranking your engine to start, but the other piece to the puzzle is the alternator. It keeps your car supplied with electrical energy when the engine is running. 
Now that we’ve answered, “what is an alternator?”, you may be wondering “what does an alternator do?” Well, it powers your car’s electrical components while driving or idling, supplying the components with Direct Current (DC) power. The alternator is also responsible for charging the car battery while driving. 
So, how does it all work? 

  • In simple terms, the alternator turns mechanical energy into electrical energy. 
  • When your engine is running, it powers a drive belt that spins a pulley attached to the alternator. The pulley turns the alternator’s rotor shaft, which spins an electromagnet around a coil of wire. 
  • The spinning electromagnets generate Alternating Current (AC) around the coil, which then flows through a device called a rectifier (inside the alternator). The rectifier is the component that converts the Alternating Current into Direct Current. 
  • The Direct Current and voltage is what is used to operate the car’s electrical system. 
  • And, lastly, a voltage regulator controls the electromagnet and ultimately controls the output of the alternator. 

So there’s the answer to “what is an alternator?” Still confused? You can always call the technicians at Jiffy Lube® with questions. They’re trained and ready to answer questions about what does an alternator do. 
Modern alternators have long lives and typically last the lifetime of your vehicle, but unfortunately failure can occur. Here are a few reasons why:

  • General wear and tear
  • Heat damage
  • Overuse
  • Exposure to water
  • Faulty parts
  • Frayed wires


What Can Happen When The Alternator Isn’t Operating Properly?

  • Your engine may not crank or may not continue running for more than a few minutes.
  • A dead car battery, since a defective alternator cannot sufficiently charge the battery while the engine is running. This causes the charge in the battery to deplete faster than usual.
  • Issues with an electrical system (if this occurs, stop into your local Jiffy Lube® to have it inspected.)
  • Dim or extremely bright lights. As an alternator begins to fail, it can provide inconsistent current/voltage to your electronic accessories. You may also experience lights that flicker or that erratically go from bright to dim and vice-versa.

Although a dead battery can be a sign that your alternator is malfunctioning, sometimes it is just the battery, and your alternator may not necessarily be the issue. This can happen when your battery has reached the end of its useful life or if you leave the headlights on all night, etc. 

Is It The Battery Or The Alternator? Here’s How To Find Out.

First, try jumpstarting your car. If your car stays running, your battery may need to be replaced, but if your car dies again shortly after, it may mean that the alternator isn't providing enough current/voltage to the battery.
Slow or inoperative electrical accessories
An alternator that isn't supplying enough current/voltage often results in slow or inoperative accessories. If the windows take longer than usual to roll up or down, or if the seat warmers aren't heating quickly, there may be an alternator issue.
Many late model vehicles are equipped with a priority list of equipment programmed into their control modules that determines where to cut power first if the alternator isn't supplying enough electricity. That way, if the alternator fails, power to your radio (or other nonessential accessories) will be cut before losing power to your headlights.
Trouble cranking or frequent stalling
Like we noted earlier, trouble cranking the engine may mean that your alternator is failing to charge the battery. When attempting to crank the engine, all you’ll hear is a clicking sound. If the engine frequently stalls out while driving, it may be a sign that the ignition system isn’t getting enough power from the alternator to keep the engine running.
Unusual noises coming from the alternator
Cars make a lot of sounds, and most are harmless, but others can indicate serious mechanical problems. With a defective alternator, you'll often hear growling, squealing, or whining under the hood. Squealing can happen when the belt that drives the alternator's pulley becomes misaligned or loose. Growling or whining can mean the bearings that support the rotor shaft are defective.
Burning rubber or electrical wire smell
A foul odor (burning rubber or wires) may indicate that the alternator is starting to wear out. This happens when the alternator's drive belt is under constant tension and friction, and since it’s close to the hot engine, it wears out over time, emitting an unpleasant burning rubber smell.
A seized alternator pulley bearing will also cause the drive belt to emit a burning rubber smell as it rubs the seized pulley when the engine is running. This can happen if the alternator is being overworked or has frayed or damaged wires. An overworked alternator produces a higher-than-normal current flow, which can cause wiring to heat up unsafely.

An illuminated battery/charging system warning light
When this light illuminates, it's commonly mistaken to be a battery-specific issue. The battery/charging system warning light indicates that there could be an issue within the car’s electrical system, including the alternator. An alternator is designed to work at a specific voltage, typically, between 13-14.5 volts. If the alternator fails, system voltage may drop below capacity (<13.0 volts), causing the battery/charging system warning light to come on.
The battery light will also appear if the alternator is exceeding its voltage limit (>14.5 volts). Depending on the electrical load, the battery/charging system warning light may flicker on and off as system voltage fluctuates in and out of its intended range.

What Happens When You Bring Your Car To Jiffy Lube®?

Stop by any of the 2,000+ locations nationwide and a Jiffy Lube technician will test your alternator by checking its charging level, the battery strength and charge, and resting voltage. Rest assured Jiffy Lube follows OEM recommendations and processes in accordance with the manufacturer’s warranty. We’ve got you covered, so you’ll be charged up and back on the road in no time. 

Jiffy Lube technician propping up a vehicle hood before inspecting the car's alternator

Read More About It.

Now that you can answer “What does an alternator do?”, learn more about your check engine light here.
Please note: Not all services are offered at each Jiffy Lube location. Please check with your local Jiffy Lube service center or visit for specific services offered.