All About Your Hyundai Alternator

From the spark plugs to the speakers, if it's electric and it's part of your Hyundai, it depends on power from the alternator. What can cause the alternator to fail, and how can you make sure your car's electrical problems are caused by the alternator, and not by something else?

The Parts of the Alternator

The alternator uses several components to convert the rotational energy of the engine into a steady source of electric power.

Pulley: the alternator is mounted to a bracket next to the engine, putting its pulley in line with the pulley on the crankshaft. While the engine is running, the crankshaft pulley transfers power to the alternator pulley via a belt.

Shaft: The shaft is attached to the pulley and extends into the body of the alternator.

Bearings: A set of sealed bearings keep the shaft and pulley in position while letting them spin freely.

Rotor: This round body of magnets is attached to the shaft and spins inside the housing.

Stators: The movement of the rotor excites the electrons inside the copper windings of the stators, generating alternating current. 

Rectifier: The diodes inside this device act like a one way valve, transforming the alternating current from the stators into direct current.

Voltage regulator: The flow of current coming out of the alternator can vary depending on engine speed, but the regulator can dampen this output to keep it within a certain voltage range.

Case: The case both isolates the electrical components to prevent a short and allows plenty of airflow to keep those components cool.

Why Doesn't the Alternator Just Make DC Current?

Direct current generators were commonplace on old vehicles, but they only work well over a very narrow speed range. It was good enough to provide electricity for lights and spark plugs, but as cars got more sophisticated, manufacturers turned to alternating current generators to provide electricity over a wide range of engine speeds to support an ever growing list of accessories. An alternator converts this AC power into DC because DC wiring is simpler.

Does My Hybrid have an Alternator?

No. Instead, Hyundai uses a combination starter/generator. A normal starter has a shaft that extends as it spins, forcing the gears on the end to mesh with the teeth on the flywheel or flexplate. From there, the force of the starter motor spins the engine until it starts. Once the driver releases the ignition, power is cut to the starter motor, and the gear shaft slides away from the teeth. On hybrids, this starter/generator combination always has the gear meshed with the motor's flexplate. Once the engine has started, the polarity switches and it becomes a generator, spinning against the flexplate to generate power.

Keep in mind that your hybrid has two electrical systems: a 12 volt system that draws from this generator and a standard 12 volt battery to power accessories and a high voltage system that is used for the drive motor and hybrid battery pack. A failing starter/generator will cause the same problems as a failing alternator, and it will also make it difficult for the gas engine to fire up when needed.

What Causes an Alternator to Fail?

In short: heat, dirt and vibration. However, these factors affect each component differently.

The alternator can overheat if the vents on the case become clogged, or something happens inside the engine compartment to drastically increase temperatures, like a fire or the overloading of a catalytic converter. 

The bearings that the shaft rides on will usually last a very long time, although high temperatures and dirt can accelerate wear. The increased friction will slow down the shaft, reducing power output and eventually causing the alternator pulley to slip on the belt. Vehicles with a serpentine belt usually have an automatic tensioner, but if you have an older Hyundai with a separate alternator belt, it's possible to overtension the belt, putting pressure on the bearings.

The wiring in the stators can break after years of being subjected to heat and vibration. Since there are multiple stators, a single break won't stop power generation, but it will reduce it significantly. Likewise, the rectifier uses multiple diodes. If one fails, the power that enters the electrical system is reduced.

Finally, if the voltage regulator fails, high voltage spikes can overload the electrical system.

How Failing Parts in the Alternator Affect Your Vehicle

When the engine is running, the power from the alternator is first sent to the battery to charge it, and then goes through the rest of the electrical system to power all the accessories. When the engine is off, the accessories just draw power from the battery. If the alternator isn't producing enough power, the battery takes up the slack, running everything until it runs out of juice. As it drains, the voltage in the system drops, causing dim lights, malfunctioning accessories and engine misfires until there isn't enough power to keep the spark plugs firing, shutting down the engine. 

A bad regulator will cause electricity to enter the system that is too high in voltage, burning out fuses and overheating the battery, boiling away the electrolyte. If this electricity does reach accessories like the headlights or gauge cluster, lights will flicker and displays will behave oddly.

Failing bearings will make grinding or squealing noises when the engine is running. 

How Do I Know My Alternator is Bad?

Puget Sound may be calmer than the ocean, but it's still full of salt water, and that means corrosion. If you live out here or anywhere near a coast, it's a good idea to inspect and clean the main connections of the electrical system, particularly the grounds and battery terminals. Corroded connectors don't transfer power well, which can make it seem like the alternator isn't working at peak performance.

Checking for bad bearings is easy: remove the belt and spin the pulley by hand. It should spin freely. If it makes noises or takes effort to turn, the bearings are bad.

Look at the drive belt while the engine is running. If it looks like it's vibrating, it's either worn out, or the belt tensioner isn't working correctly. A loose belt will keep the engine from driving the alternator effectively, causing the same symptoms you'd find with failing stators and rectifiers.

Using a multimeter, check the current by touching the probes to the battery terminals. If the battery is hard to access, touch the positive probe to the where the large power wire connects to the alternator and the negative probe to a bolt on the frame. With the engine running, the voltage should be very close to 14 volts. The alternator may be failing if output is under 13 volts, and the regulator is failing if it's above 15 volts.

If the voltage was low in the last test, shut off the engine and check the battery voltage. It should be near 12 volts, but a reading of 10 volts or less in warm weather or 9 volts or less in cold weather indicates a failing battery.

Where Can I Get a Quality Alternator?

With so much riding on this component, it's worth getting the best. HyundaiPartWorld.com carries only OEM parts, built by Hyundai to meet their own design and quality requirements. That means you'll get a part that's just as reliable as the one fitted at the factory, and it's even backed by a warranty from the automaker. Our site lets you search for parts based on your model and VIN as well as part numbers and keywords. Have questions? We have experienced parts people who can help.