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Alternator: main failures and how to prevent them?

As it happens with most parts, we only notice an alternator problem when it fails. When we try to start the engine and the car won’t start, or when the battery light comes on in the dashboard.

And, why is that?

Because the alternator transforms the mechanical energy, produced by the engine, into electrical and supplies it to the electrical components in your vehicle. So, any failure in the alternator results in the battery weakening faster.

For this reason, it is essential to keep the car’s alternator in optimum condition. Be aware of the warning signs to avoid more significant problems in your vehicle.

And don’t worry, we can help. We present in this article the main “symptoms” and tips to prevent possible problems with this part of your car.

Read also: Alternator: what is and how it work

Signs indicating alternator problems

Alternator problems are not uncommon. The hardest part is identifying possible faults in this element from the outset.

As the alternator maintains the battery’s charge level, any problem is easily mistaken for a battery fault. Also, when this component is not working, it’s the battery light that comes on in the dashboard.

Hence, it is typical to confuse the problems in these two parts.

Also, pay attention to your car’s lighting and air conditioning system. The alternator ensures the operation of these systems, so any instability may represent possible problems in this part.

Thus, the main signs that reveal alternator problems are:

  • discharged battery;
  • difficulty starting the car on the first try;
  • intense noise in the transmission belt;
  • burnt rubber smell due to the alternator belt rubbing against one of the components;
  • dimming of headlight intensity or even burnt headlights;
  • oscillation in the intensity of the car’s interior lights when the stereo is on;
  • slowness when opening and closing the electric windows;
  • and, as mentioned earlier, battery light on the dashboard or flashing. This light comes on when you place the key and may remain on even when you turn the key off.

The alternator tends to fail gradually, and diagnosing these signs early can prevent problems and higher costs. You don’t just run the risk of your car being left stranded or without air conditioning. Alternator failures can stop the power steering and lighting system from working.

So don’t ignore these signs and repair the problem as soon as possible.

Dashboard of a car with the battery and engine lights on

Causes of engine alternator failure

Now that you know how to identify possible alternator failures, you should also understand the causes of these problems.

Because the alternator doesn’t only fail due to flaws in the elements. Other problems may result from poor management by the driver.

Find out in detail the principal causes.

Friction on internal moving parts

Alternator operation involves high-speed rotation, which can wear out components over time, particularly the bearings and brushes. When this happens, they will exhibit resistance to movement leading to a potential overload on the other elements.

So, be aware that it is not enough to replace the bigger components, such as the rotor or the stator. It is also necessary to take care of and replace the smaller parts, which can be the source of the problem.

Short circuit

How many times have we helped other drivers on the side of the road to charge their car batteries?

If this isn’t done in the right way, i.e. if the position of the cables is wrong, the battery short-circuits and causes permanent damage to the alternator.


Alternator operation is affected by an overload due to excess consumption. In other words, it is influenced by the disproportionate effort required to compensate for the energy used by the driver.

This happens when the alternator is not working to offer mechanical energy for electrical conversion. For example, when the radio is on without the engine running.

At the same time, overloading also occurs when various electronic extras are installed in the car, such as speakers and xenon headlights. In these cases, the power demanded by these accessories is much higher than the power supplied by the original alternator.

Alternator belt breakdown

Alternator belts are made of rubber. Over time and with constant stress, this component starts to lose its elasticity until it eventually breaks completely.

If the belt breaks, the part and the vehicle’s condition are compromised. In addition to the alternator stopping generating power for the battery, the water pump also stops spinning, increasing the risk of the engine overheating. The air conditioning and power steering may also stop working if they aren’t driven by their own chain.

So if the alternator belt breaks, you should replace the part immediately to avoid more significant problems in your vehicle.

Electrical overload

Alternators are made up of voltage regulators, which are essential for the safe operation of the electrical system.

If the regulator is damaged, it will not analyse the variations in energy levels produced by the engine. Consequently, the charge levels will be converted into equal electrical currents, transferring a violent load to the car’s electrical devices. This can cause permanent damage to the electrical elements.

To check for possible flaws in the voltage regulator, the mechanic can measure the alternator charge on the battery with a multimeter. If the battery is above 15 volts, the regulator is likely damaged.

Read also: Engine Control Unit: what is, the features, and possible failures

How to prevent alternator problems?

As you have noticed, there are alternator problems that can be avoided.

We present below some tips that can help you conserve this part and increase its durability.

Carry out regular maintenance

The first and foremost care you should take with your car’s alternator is to check it serviced regularly. This is the only way to know if all the components are in good condition and change them if and when necessary.

In the case of the belt, it is recommended to check its condition every six months. This will ensure that it doesn’t have any breaks or is overstretched or loose.

Managing your car battery correctly.

First, avoid leaving the car stopped for a long time, i.e. for more than 20 days. As electronic devices are left on standby, they slowly consume the battery.

Second, do not use the radio or other electronic devices with the car engine off. This behaviour only accelerates the discharge of the battery, causing it to overcharge and damage the voltage regulator because the alternator has to release more energy to compensate.

Avoid excessive electrical accessories

A high-powered sound system, electric windows and xenon headlights are accessories any driver would like to see in their car. But before installing them pay attention to the capacity of the car’s alternator and battery.

These components require more power than the original alternator can supply. So if you want to add electronic extras, you should also replace the battery and alternator for ones with higher amperage.

Read also: 10 Myths about cars: Part 1

Alternator exposed on white background

When to replace the alternator?

It is common to ask how often we should replace car parts, like every how many km or year. This question is logical if we think about tires, timing belts, oil, etc.

However, when we talk of the alternator, there is no way to answer with a number of years or km of when it should be changed. In fact, the whole part may never be replaced. It is more common to change one of the components of this part.

For example, brushes, bearings and the belt are elements that wear out over time. The voltage regulator is also an item that can be damaged in isolation. So, in these cases, it is better to replace these components than buy an alternator.

However, if the rotor burns out, it may be preferable to purchase the entire part rather than repairing this element.

In short, be attentive and concise. Carry out the recommended servicing and inspect the condition of the alternator and its components. Only by regularly checking and managing your car properly, you can prevent possible problems with your car’s alternator.