Role of the Alternator
The alternator is a device that generates electricity by using the engine’s rotation. It supplies power to electrical components in the car such as headlights, the navigation system, and the air conditioning. It also charges the battery. While the engine is running, the alternator provides most of the electricity used in the vehicle.
Main Components
- Pulley
- Rotor (a rotating electromagnet)
- Slip rings and brushes
- Stator coil
- Diode (rectifier)
- Voltage regulator
- Cooling fan
- Housing (case)
Structure and Operation of Alternator
- When the engine starts, the rotation of the crankshaft is transferred via a belt to the alternator’s pulley.
- This rotation turns the rotor inside the alternator. The rotor functions as an electromagnet by receiving excitation current through the slip rings and brushes.
- As the rotor spins rapidly, it creates a changing magnetic field around the stator coil.
This changing magnetic field induces alternating current (AC) in the stator coil.
Since the car’s battery and electrical components operate on direct current (DC), the diode (rectifier) converts the AC into DC. - Next, the voltage regulator keeps the voltage stable, ensuring a steady power supply to the battery and electrical systems.
- Because the alternator spins at high speeds, it generates heat inside. To cool it down, a built-in cooling fan draws in air to dissipate the heat.
All these parts are enclosed within the alternator’s housing.
Common Symptoms and Causes of Alternator Problems
Common Symptoms and Possible Causes of Failure
- Battery Warning Light Turns On
- Low alternator output (due to a faulty regulator or worn-out brushes)
- A loose or broken belt
- Poor electrical connection (such as damaged or corroded wires)
- The regulator sending out abnormal voltage
- Battery Frequently Dies (Even After Replacing with a New One)
- The alternator is not charging properly (low voltage or current output)
- A faulty stator coil or diode in the alternator
- Parasitic drain (something is using power even when the ignition is off)
- Corroded or loose battery terminals
- Engine is Hard to Start or Won’t Start
- The battery is not charged due to a faulty alternator
- A weak or dead battery
- Damaged or corroded battery cables
- Headlights or Electrical Components Work Unreliably
- Unstable output voltage (faulty voltage regulator)
- Worn slip rings or brushes
- Low alternator output
- Faulty diodes
- Unusual Noise from the Engine Compartment
- Worn or damaged bearings inside the alternator
- Squealing drive belt (too tight, too loose, or worn)
- Broken or rubbing cooling fan
- A Strong, Sharp Smell
- The alternator is malfunctioning and supplying too much power to the battery
- Steering Feels Heavy While Driving
- The alternator is faulty, causing the electric power steering (EPS) assist to weaken or stop working
- Engine Stalls While Driving
- The alternator is not producing enough power, so the electrical system doesn’t get enough electricity
- The ECU shuts down to protect itself from overvoltage or overcurrent
- The battery is completely discharged