If you’ve heard the term “alternator” before, you probably know that it’s an important part of your vehicle. But what exactly does an alternator do? In short, an alternator can charge a car’s battery, allowing you to start your car and use electronic accessories.
If you’re having problems with your car’s alternator, you may find that your car won’t start or runs continuously for more than a few minutes. You may also experience abnormal batteries, accessories, and lights. Before any of the above happens, though, you may experience one or more of the seven signs of alternator failure.
Read on to find out how to find a faulty alternator before you get stuck.
7 Signs of an Alternator Failure
Your battery provides the power needed to start the engine. In return, the engine rotates the alternator pulley, which keeps the battery powered while the car is moving. The alternator is the bridge between these two components.
Since the battery cannot power the engine and electrical accessories indefinitely, an alternator is required to convert the engine’s rotational power into electrical energy. If there are any issues with this charging system, you will notice at least one of the following adverse alternator symptoms.
1. Battery Warning Light on the Dashboard
When a battery warning light appears on the dashboard, it is often mistaken for a battery-specific issue. However, battery warning lights often indicate that there may be a problem with your car’s wider charging system, including the alternator.
The alternator operates at a specific voltage, usually between 13-14.5 volts. If your alternator fails, its voltage may drop below capacity, causing a battery warning light to appear on the dashboard. Similarly, if the alternator exceeds its voltage limit, a battery indicator may also appear, depending on how much pressure it is subjected to.
Depending on the electrical load of the car accessories (headlights, wipers, radio, etc.), you may see the battery warning light flashing as the alternator fluctuates up and down at its expected voltage capacity. While this may seem like a minor annoyance, the light will never blink if the alternator is in good condition and the engine is running. In this case, it’s best to send your car for an alternator check rather than ending up stuck on the side of the road.
2. Dim or Excessively Bright Lights
When the alternator or alternator’s voltage regulator starts to fail, it can provide inconsistent voltage to your electronic accessories.
In general, this manifests itself as poor or overly high device performance, such as headlights that are too dim or too bright. You may experience flashing lights or erratic changes in light from bright to dark, and vice versa. Overloaded lamps can also fail prematurely, especially if the problem is not resolved quickly.
3. The Battery Is Dead
Sometimes, a dead battery is just a dead battery — which reaches the end of its useful life after a few years of use — or it could be that the headlights have accidentally been on all night. Sometimes, however, a dead battery can be a sign that your alternator is malfunctioning.
A damaged alternator fails to adequately charge the battery while the engine is running, causing the battery to drain faster than usual. One way to test if the battery or alternator is damaged is to start the car. If you start your car the right way and it stays running, your battery may need to be replaced as soon as possible. However, if you start your car quickly, and the car stalls again shortly after you disconnect the jumper cable, your alternator may not be able to provide enough power to the battery.
If your battery only runs out at night or when the car is parked with the engine turned off, the rectifier of your alternator may be faulty. The alternator produces alternating current (AC), but car batteries require direct current (DC). If the rectifier is working properly, it will convert alternating current to direct current by restricting the flow of current in one direction.
However, if the rectifier diode fails, the current may flow in both directions. This means that the alternator will actually drain the battery! If the diodes on the rectifier do not stop the current from flowing back, then when the engine is turned off, the battery will supply power to the alternator, thus draining the car’s battery.
4. Slow or Faulty Accessories
The alternator is not able to provide enough power to the car’s electronics, often resulting in accessories running slowly or not working. If you notice that your windows are taking longer than usual to rise or fall, or your seat heater feels “closed”, or even if your speedometer and other instruments start to get out of control while the vehicle is moving, you may be experiencing an alternator problem.
Many modern vehicles also have a priority list of devices programmed into the car, which tells the on-board computer where to cut off the power first if the alternator can’t provide enough power. That way, if the alternator you’re using while driving fails, you may lose power (or other non-essential accessories) before your headlights go off.
5. Difficult Start-Up or Frequent Pauses
A faulty engine start may mean that the alternator is unable to charge the battery. This means that when you turn the ignition key, you’ll only hear a click, not the grunt of the engine.
On the other hand, if your car is frequently stalling while driving, and you notice that the battery indicator light is on, it could be a sign that the control module is not getting enough power from the alternator to keep the engine running.
6. Roaring or Whining Sounds
Cars make a number of strange noises – some are harmless, while others can indicate a serious mechanical problem. If you hear a roaring or whining noise coming from under the hood, there may be an alternator issue or other drive belt issue that should be checked by a professional as soon as possible.
This growling or whining sound occurs when the belt that turns the alternator pulley is misaligned or rubbing against the side of the pulley. You may also hear this sound if the bearing of the rotating rotor shaft is damaged.
7. The Smell of Burning Rubber or Wires
A foul smell from burning rubber or electrical wires may indicate that parts of the alternator are starting to wear out. Since the alternator’s drive belt is under constant tension and friction, and because it is close to a hot engine, it may wear out over time and emit an unpleasant smell of burning rubber.
Similarly, if your alternator is overworked or the wires are worn or damaged, you may smell a burning smell similar to an electrical fire. An overworked alternator tries to deliver too much power through the wires, causing the wires to heat up unsafely. Damaged wires can also create resistance to the current, causing the wires to heat up and emit an unpleasant odor.