Alternator: What is it? What symptoms does it show when it breaks down?

Most drivers know the most basic and essential elements of their vehicle. Components such as the engine block, transmission, battery, and alternator. We know that the former creates the propulsion to start moving, the transmission keeps the vehicle moving, and the battery helps get that whole process started. But what does the alternator do then?

Roughly speaking, the alternator is the boss when it comes to generating power. Sure, the battery is the one that initially powers the whole shed, but once that cycle is complete, its job is done until the next time the engine needs to be started. It takes a lot of energy to start a car and keep it running, and that’s where the alternator comes into play, creating and continuing to supply power to the battery, as well as the various electrical components that make up the miles of wiring for almost any vehicle.

Until the 1960s, cars used DC dynamo generators with commutators. With the availability of more affordable silicon-controlled rectifiers, alternators came into use. This change was also encouraged by the increasing demand for electrical energy required in this period, increasing loads thanks to larger and more powerful headlights, electric windshield wipers and windows, heated rear windows, and other accessories of various kinds; Today, cars are computers on wheels.

The modern alternators as we know them today were first used by WWII military vehicles to power radio equipment. After the war, other vehicles with high electrical demands, such as ambulances and taxis, would also be equipped with alternators. But it would not become part of the standard equipment of a production model until 1960 in the Chrysler Valiant, several years before the other two big ones of Detroit – Ford and General Motors – began to introduce them in their cars.

How does a car alternator work?

The alternator is a relatively simple component that contains only a few parts, but it plays a critical role in the operation of any combustion vehicle. The alternator converts the mechanical energy of the crankshaft into electricity through induction. The wires inside it pass through a magnetic field, which in turn induces an electric current. This current is used to power the car accessories, from the headlights to the automatic opening of the trunk (if your car equips it).

The alternator also keeps the battery fully charged, providing the power it needs to start the vehicle. It is usually bolted close to the engine’s front and is driven by the crankshaft via the auxiliary belt. The part itself contains smaller components to help generate power:

  • Pulley: The element that receives, through a belt, the mechanical force generated by the car engine. It is attached to the alternator shaft and is intended to move the rotor inside.
  • Stator and rotor: they are magnets located inside the alternator that rotate to create alternating current and convert energy into electricity.
  • Diodes: They transform alternating current into direct current to charge the battery and allow current to travel in only one direction, from the alternator to the battery.
  • The voltage regulator Prevents power surges by ensuring that the voltage is kept in the proper range.
  • The cooling fan: It is located on the inside or outside of the alternator to protect the internal components from overheating by dissipating the heat generated from the formation of energy.

What are the symptoms of an alternator starting to fail?

It all starts with some subtle problems, like a light in the instrument panel that comes on for a brief moment, headlights that dim their beam intermittently, or turning the key makes the car screech when starting. Even other electrical systems such as the windows may not work correctly, the car itself may give off a strange smell, or you may hear an annoying noise coming from under the hood. Next, we will unravel what are the possible symptoms of an alternate in lousy condition.

The warning light in the instrument cluster

Inside the instrument cluster of most cars built in the last decade, there is a dedicated warning light to signal a problem with the alternator. It is usually described in the shape of a battery, although it is sometimes shown by the acronym “ALT” or “GEN,” which stands for alternator or generator, respectively. Many people instinctively believe when they see this warning that they have a problem with the battery, which is a symptom that will be discussed later, but that is not why the light comes on.

It’s tied to the computer systems that monitor the alternator’s voltage output. If it falls below or above a preset limit, the light turns on. If it is within range, the light remains off. In the early stages of alternator problems, the light may appear to blink. Most of them have an output between 13 and 14.5 volts. As more power is demanded when activating things like the windshield wipers, radio, or headlights, the alternator needs to work harder to keep the voltage constant.

Dim or flickering headlights

If the lights are dimming or blinking, it means that the alternator is not generating enough electrical power to keep them running at total capacity. As the engine speed increases or decreases, the headlights will brighten and dim as the current output from a weakened alternator periodically increases and decreases. The reason is that a unit in good condition always keeps the headlights at their maximum brightness regardless of the engine speed.

Other electrical faults

When the alternator is malfunctioning, other systems that work with it can begin to fail. These can include power windows, central locking, instrument panel lights, air conditioning, and even stereo. Of course, any of these functions may be interrupted at any time. Motors fail, cables are crossed, and all kinds of faults can occur. If you notice an electrical peculiarity, or several at once, it is probably not a coincidence. If this is the case, take it to a trusted workshop.

Strange Noises

If the alternator fails, some of the engine’s bearings may fail, creating rattling and unusual sounds, something like a grinding noise. It can also be felt when the belt that turns the alternator pulley becomes misaligned, worn or cracked, or rubs against the side of the pulley itself. Locating this problem while standing is simple, as it can be seen with the naked eye, but if it were the case that we were running and it broke, we would hear an unpleasant noise, and some parts of the alternator could even come off.

The battery is dead.

Batteries sometimes fail independently, but a faulty alternator can cause them to drain sooner because it simply won’t recharge. If you are not sure if it is the battery or the alternator that is the cause of the electrical failure, you can try using a pair of tweezers. Start the car and remove the cables immediately. If the alternator cannot maintain the system and the vehicle shuts down instantly, the alternator fails. If the vehicle continues to run after several minutes, the battery is likely the culprit.

The car stalls or is hard to start.

As mentioned above, problems starting the car can mean that the alternator is not charging the battery. That means when you turn the key in the ignition, all you will hear is a “click” rather than the pleasing purr of the engine. On the other hand, if your car stops relatively frequently while you’re driving, this may be a sign that the spark plugs are not receiving enough power from the alternator to keep the engine running. In other words, the battery isn’t dead yet, but it’s on its way.

Strange smells

Belts that do not rotate can produce a burning rubber stench due to increased friction. A belt that slips on the alternator pulley will smell more like an electrical fire, indicating that the belt needs to be adjusted. If it has already been changed, a mechanic should test its operation. Likewise, an overworked alternator will try to push too much electricity through its wires, causing them to heat up. Damaged cables create resistance to electricity flow, causing them to heat up and emit an unpleasant odor.

Can I make a visual diagnosis of the state of the alternator?

If you notice any of the unusual behaviors described above, take a look under the hood for a visual inspection of the alternator belt. Look for signs that have a crystallized or burned appearance. A loose belt can slide over the pulleys, causing friction on metal-to-rubber contact, which in turn heats the rubber and causes the belt to wear out faster. To solve the problem, tighten the tensioner. However, overtightening can lead to damage to the alternator components.

What is the lifespan of an alternator? How much does it cost to replace it?

An alternator is a component that does not need maintenance. It can last up to 10 or 15 years without problems in some vehicles, or between 200,000 and 400,000 kilometers. If it fails, the car may still be able to run for a short time on battery power. However, the engine will stop as soon as its reserves are depleted. Replacing an alternator costs between 400 and 600 euros if we talk about the manufacturer’s original unit (OEM), which does not exactly make it a “cheap” part.

However, there is an alternative: a reconditioned alternator. It may well be that of your car if it can still be saved or that of another that has passed to a better life (to a scrapyard, for example). It may take longer, but it is generally cheaper, as you only pay the price of labor (between 30 and 100 euros) plus the charge for the “new” alternator (between 50 and 200 euros). Whenever it is replaced, it is also a good idea to change the timing belt as it has to be removed to access the alternator and is not too expensive.

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