Alternator not charging battery but alternator is good: [Causes,Reason & Fix Solved]

Every time you turn on your car, the alternator is responsible for providing power to the vehicle’s electrical system. The alternator provides power when the engine is running, and charges the battery when the engine is off.

There are many things that can cause an alternator to fail, but there are two main causes that account for most situations: worn carbon brushes and a bad alternator itself.

A worn out alternator can be identified by listening to it while it is running. If you hear lots of noise coming from it, then it is likely due for replacement.

Worn carbon brushes will also produce a lot of noise when they are running and are usually replaced at the same time as the alternator itself. Let’s check what would cause a good alternator not to charge?

6 Causes of an Alternator not charging battery but alternator is good

Causes of an Alternator not charging battery but alternator is good

This guideline shows you how to discover and fix Most Common Causes of Your Alternator Not Charging and How to Fix Them.

It also provides simple procedures, schematics, tests, diagnosis, and repair advice for automotive systems like the engine fluides, exhaust system, cooling system, wiring diagrams, brakes, suspension and steering.

#1. Computer Error

If there is a computer error with your vehicle, it will result in a weak electrical system. This can cause your lights to dim and may even shut off completely.

A computer error will cause your voltmeter to read “0” volts. This can also be caused by a failed voltage regulator or a faulty voltage regulator bypass module located on top of the alternator.

 It also causes your battery to not charge properly, which means your battery doesn’t have sufficient power for you to start your car. In severe cases, it may prevent you from starting your vehicle at all.

#2. Broken Belt or Pulley

A belt or pulley problem can cause you alternator to stop charging when there is a slipping noise. If you have broken belts and pulleys, this can cause your alternator to overheat and stop charging.

A belt or pulley problem can cause your alternator to stop charging when there is a slipping noise. If you have broken belts and pulleys, this can cause your alternator to overheat and stop charging.

If your belt or pulley breaks, it can cause stress on other parts of the car while it’s moving. This extra movement may cause other problems, including an alternator that isn’t charging properly.

#3. Worn carbon brushes or a damaged alternator itself

The battery sends power to a regulator, which in turn regulates how much power is sent to the alternator. If the regulator fails, there isn’t enough current to charge the battery, and the voltage drops.

This is a common problem when driving through mountainous terrain. The second most common cause is the alternator itself.

Over time, carbon brushes wear down and eventually lose contact with the rotor, making them unable to transmit power to the battery.

Keep in mind that these problems usually don’t occur all at once. If you’re having trouble charging your car, try checking these first before replacing any of your components.

#4. Blown Fuse

A blown fuse can be very difficult to diagnose because there are so many places a fuse can be located in a vehicle.

If your fuse box has blown fuses, it could be shorting out the wiring in the vehicle’s electrical system including the alternator.

A blown fuse in your circuit breaker panel may not visibly show damage but will still be evident as an open circuit. However, if your lights are dimming or flickering, you may have a blown fuse that’s causing the problem.

#5. Wiring Issues

Wiring issues can cause your alternator to not charge if there is a loose or damaged wire in the system. The wires are usually black and white with red being positive and black being negative.

This is why it is important for you to check for signs of physical damage before you check the wiring connections inside of your vehicle’s ignition system.

#6. Overheating Issues

The alternator can overheat or fail under certain circumstances, causing it to not produce enough electricity. The most common reason for an alternator to overheat is a lack of coolant.

When there is not enough coolant, the alternator will get too hot and will not produce electricity at its full capacity.

What Is an Alternator?

What Is an Alternator

Alternators are installed on vehicles so that they can harness the power of the engine and provide it to the batteries. It is a device that converts mechanical energy into electrical energy.

A belt-driven by the engine turns a rotor inside the alternator, creating an electromagnetic field that induces a high voltage in the stator windings. The stator windings are then connected directly to the car battery.

The alternator is normally located on top of the engine and you should check it if your battery is not being charged when you have your vehicle running. Other causes for charging issues are a broken belt or pulley, blown fuses, wiring issues, and even computer errors.

There are two main parts that wear out on an alternator, the bearings and carbon brushes. The carbon brushes are what actually make contact with the rotor inside of the alternator.

The rotor spins when you start your engine and charges up your battery as a result. Carbon brushes generally last about 100k miles before they need to be replaced.

How to Fix?

The first step is to check the fuse box for burnt fuses. If you find any burnt fuse, replace it with a new one. The next step is to check the alternator by using a multimeter tool that can measure electric current.

Then connect the positive cable from the battery to the multimeter, and then connect one side of the red probe from the multimeter to the positive cable and then connect the other red probe to one of the terminal on the alternator.

Then do the same thing but this time you connect both of the red probes from your multimeter to both terminals on your alternator.

If you do not see any reading on your multimeter, then you need to check your voltage regulator because most likely it is faulty or shorted out.

Then lastly you need to check your battery by doing the same thing that you did with your alternator but this time instead of connecting it directly to your alternator, you need to disconnect the negative cable from the battery and connect it directly to your multimeter.

The reason why you have to put the multimeter on the terminals is that they are hot. You don’t want to touch them with your fingers. If you do, you can get a shock, burn yourself and even start a fire.

It’s easy to fix this problem but it takes time and patience.

When you check the fuse box for burnt fuses, there could be two problems. The first one is that another device may be drawing power from the battery or it may be a short in the wiring system.

The second problem is that the alternator is not charging the battery and there is no juice going into the fuse box.

When checking the alternator, you have to make sure that it’s not sending voltage to other devices or lighting up wires or relays on its own. If it does, then there is a short in the alternator or wiring.

This can also cause some electrical devices to light up at night when the car isn’t running like radio lights and dashboard lights.

You will need to know if your car has a voltage regulator. This is a device that regulates or controls voltage to the battery. If your car does have one, then you need to check for blown fuse links on the regulator. Also, check for bad connections at the alternator and battery terminals.

If your car does not have a voltage regulator, then you need to check for loose wiring harness connectors at both ends of the wire harness connecting from the alternator to the battery.

And also make sure that these wires are not touching any grounded part of the body or chassis of your car.

After checking these things you can know if it is a bad alternator, a bad voltage regulator, or bad connections on either end of the wire harness that connects from alternator to battery.

Tips: A burnt-out alternator should be replaced as soon as possible because without it, you will not have any electricity in your car and your battery will die. If you do not replace your alternator quickly, you may damage other parts in your cars such as your headlights or even more expensive things like computers and radios.

Alternator Clutch Pulley Symptoms


The most common reason for the alternator to fail is that it’s just worn out. Worn brushes, bushings, and bearings will cause the alternator to overheat and not work.

The other common problem is a bad belt or pulley. While most of these problems can be diagnosed fairly easily, the real challenge lies in getting to the root of the problem and correcting it.

When you take your car in for service, many times they will replace parts without trying to find out what caused it to fail in the first place. You might wind up with another alternator dying on you soon after it was replaced

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