What causes an alternator to go bad

The alternator in your vehicle is likened to the mitochondria of a cell. Like mitochondria, the alternator is the powerhouse of your vehicle. It plays a vital role in the electrical functionality of your vehicle. Without an alternator in your vehicle or the presence of a bad one, your car’s battery cannot do much in powering your vehicle.

The alternator charges your vehicle’s battery and gives power to the electrical elements in your vehicle. The alternator does this by turning the mechanical energy from the crankshaft into electrical energy. This newly generated energy keeps your vehicle’s battery charged and a charged battery allows your vehicle to start.

Now, when your vehicle’s alternator goes bad this process is altered and your vehicle will rely solely on its battery to meet its electrical needs. However, your car’s battery won’t be able to take on the burden for long since it is not receiving electricity either. 

Now, car alternators do go bad. They may do this abruptly or give some warning signs overtime before they do. Thus, today we will uncover some causes of a bad alternator and a few warning signs a bad alternator gives.

Reasons why a car alternator fails

1. Damage In the Inner Components of the Alternator:

The basic component of an alternator is its stator, rotor and regulator. These three work together to supply power to the alternator and are made of diodes. These diodes are susceptible to damage, they may fail to function and may breakdown over time. When this happens, the functionality of the alternator begins to alter. Thus, affecting the way your vehicle’s electrical component works.

2. When the Alternator Has Exceeded its Lifespan:

Just like any other electrical device that has a timeframe within which it works best, so does an alternator. Generally, an alternator is expected to last 6 to 8years. Hence, when it is still in use longer there are high chances for it to malfunction. Thus, giving your vehicle electrical problems. However, some alternators may not last up to 5years before they get worn and overworked.

3. When There is a Problem with its Belt or Pulley:

Pulleys and belts are easily damaged. An alternator with a pulley or belt that is too tight, loose or broken is bound to fail. Alternators electricity for your vehicle through the mechanical energy of a rolling belt and pulley.

A loose belt slips off as it rotates, too tight a belt causes much friction and will eventually tear and a broken belt is of no good. Thus, a malfunctioning belt means mechanical energy will not be generated and with no mechanical energy, there is nothing for the alternator to work with. 

4. Poor Voltage Supply to the Alternator:

For electrical currents to be generated by an alternator it needs a field voltage of 12volts to 14volts. Any lower field voltage means the alternator will not have optimal performance. Also, the electricity generated will be poor.

5. Alternator Becomes Overwhelmed:

In the course of remodeling your vehicle, the installation of electrical devices on your vehicle that overloads its alternator will cause the alternator to fail. Thus, it is important to check that newly installed car accessories are compatible with the vehicle electric source.

6. Alternator Bearings Become Faulty:

 The rotor in the alternator rotates and generates electricity with the bearings. Usually, the bearings perform their function noiselessly but when they become faulty you get to hear rumbling noise from your car’s alternator. At this point, your car’s alternator needs to be changed.

7. The Vehicle’s Computing Unit Develops An Issue:

New model vehicles come with a computer system that controls most of the vehicle’s functions. A fault in these systems may disrupt how well the car’s alternator functions. It could alter the converting power of the alternator thus resulting in an electrical problem in your vehicle.

How to know an alternator has gone bad

Oftentimes, a car’s alternator fails abruptly. However, if it goes through a gradual failing process there are some signs the alternator may give to show it is failing or going bad.

1. Signal from the Indicator Light:

New model vehicles come with a battery-shaped indicator light tagged ALT or GEN. These lights often give the first signal to tell you that your car’s alternator is failing. It is important not to ignore this sign as it indicates whether or not your vehicle is getting enough electricity.

2. Flickering Headlights:

When your alternator is starting to fail it affects the headlights. This is because the alternator does not generate enough electricity to keep it on. A dinner headlight or an unstable one shows there is a problem with the alternator functioning.

3. Struggling to Start your Vehicle:

If your car has enough fuel and your car’s battery is relatively new but you experience difficulty getting it to start, then your alternator just might be failing. A failing alternator does not have enough electricity to get the vehicle started.

4. Failing Electrical Functions:

With a bad alternator comes failure in the performance of the car’s electrical component. The air conditioner starts failing, the windshield begins to malfunction, the radio and television start wavering even the locks get affected. When you see these signs, your alternator might be going bad.

5. Drained Battery:

An alternator powers the car battery and gets it charged. If your car’s alternator gets faulty the battery will drain more rapidly because it is not receiving enough electricity from the alternator and may eventually die. Pay attention to your vehicle if you frequently have a dead battery, your car’s alternator might need to be replaced.

6. Unusual Car Sounds or Noise:

When your vehicle starts making rumbling or cranky sounds, your alternator might have a problem. You must find the cause of the noise and rule out your alternator as being the cause. However, if it is you need to replace the bad alternator with a good one.

What is the risk of driving with a bad alternator?

Driving with a bad alternator especially when on a highway is not advisable. Yes, your car can start and move with a faulty alternator and a good battery but the car’s battery will be overworked with the electrical needs of your vehicle.

Remember the battery is not being charged at the moment hence there is a high chance it will move only a distance before shutting down. You are at risk of getting stalked in the middle of the road with a dead battery and a bad alternator.

How much does an alternator cost?

The price of an alternator varies depending on your car’s model, the alternator size, and the amp you want. Prices may range from 150dollars to 300dollars without including the cost of labor. Installation time may take about 3hours depending on where the alternator is located in your vehicle.


There are several causes of a bad alternator and oftentimes it goes bad without a warning. However, when it gradually fails you will know from the malfunctioning of the electrical components of your vehicle. Consider swiftly replacing your alternator when it is confirmed to be bad.