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Brush Function on Starter Motor

Brush Function on Starter Motor

When turning the motor key to start the engine, there is a very important process that occurs in the motor engine. One of the key components in the process is the brush on the starter motor.

Well, in this article, we will discuss the important role and function of the brush on the starter motor in running the engine. In addition, how the brush functions as an initial mover of the motor vehicle engine.

What Is a Brush on a Starter Motor?

Brush motor starter is a small motor engine component but has a very important role. Brushes are made of conductive materials, such as carbon other solid materials.

This brush is placed inside the starter motor and serves as a connector of electric current from the power source to the starter motor commutator.

Brush Function on Starter Motor

What is the function of the brush on the starter motor? The function of the brush starter motor is to flow electricity from the field coil to the armature coil, then to the commutator, and finally to the mass. The brush is a very important component.

The armature function of the motor starter is to convert electrical energy into mechanical energy, create torque to rotate the internal combustion engine, drive the starter gear, and release it after the engine is running.

While the field coil function on the starter motor creates a magnetic field that drives the armature, allowing torque to start the internal combustion engine or equipment.

If ignored, the starter motor will have difficulty starting or even cannot be started at all.

The brush on the starter motor is made of soft copper and carbon which can wear out over time because the brush will come into contact with the rotating commutator.

Preferably, if you have to choose, it is better to wear brushes than commutators, because the price of a motor starter brush is more economical than replacing a worn commutator.

What is the function of the carbon brush on the motor starter? The brush on the starter motor is placed in the main part of the motor with a series of brushes that function as a connector of electricity to the dynamic conductor through the static conductor.

In other words, the brush conducts an electric current from terminal 50 to the armature coil.

What is the number of brushes on a typical motor starter? There are two types of brushes found on the starter motor, 2 positive brushes, and 2 negative brushes.

The impact of a brush that wears out when in contact with a commutator is an increase in resistance that hinders performance. As a result, the flow of electricity does not reach maximum condition, which has an impact on the performance of engine speed that is less than optimal.

What causes the brush on the starter motor to wear frequently? There are several main reasons why Carbon Brush runs out quickly:

  1. The quality of the material is not good, which makes the brush heat up quickly and even flammable due to extreme friction.
  2. Excessive use of the engine, forced too long, and improper use can also cause brushes to wear out quickly.

Worn Brush Impact

After understanding the function of this brush, it is also important to understand the impact that occurs when the brush wears out. This is very important to prevent potential damage.

When the brush wears out, the result is its merging with a commutator that is not optimal.

This condition results in increased resistance which reduces the efficiency of conducting electricity. Electric flow that does not reach the maximum level can interfere with engine speed performance, maybe even make it difficult for the car to start.

How Does a Brush Work in a Starter Motor?

Here's how the brush works as one of the components of the starter motor:

  • Connecting to a Power Source: When turning the key to start the engine, electric current from the vehicle battery is passed to the starter motor.
  • Traversing the Commutator: The brush then pushes an electric current across the commutator. A commutator is a rotating ring connected to the rotor of the starter motor.
  • Creating Electrical Contact: When the brush touches the commutator, it creates stable electrical contact. This allows electric current to flow from the battery through the brush to the commutator, and then to the rotor of the starter motor.
  • Generating Rotation: The electric current flowing through the rotor of the starter motor generates an electromagnetic force that causes the rotor to rotate. This rotation drives the starter gears which then connect the vehicle's engine.
  • Engine Life: With enough revolutions, the vehicle's engine starts to function, and the starter motor brush plays an important role in this process.

When do carbon brushes need to be replaced? Replacing the starter motor brush or starter brush is part of the maintenance that is important to maintain motor performance.

The right time to replace the motor brush depends on several factors, including the type of motor, frequency of use, and working conditions.

1. Brush Size

If the starter brush is too short and leaves little material, it is a sign that it is time to replace the brush.

Brushes that are too short will not result in good contact with the motor commutator, which can cause problems in motor performance.

2. Ampere

If the motor is constantly running at high currents, the starter brush will wear faster. If using the motor for heavy loads or for repetitive tasks, it is necessary to change the starter brush more often.

3. Routine Maintenance

Typically, starter brushes can last for several years with good regular maintenance. This involves cleaning the brush and commutator, checking the condition of the brush periodically, and replacing it if needed.

4. Condition Monitoring

If there are symptoms such as sparks, noise, or inconsistent motor performance, this could be a sign that the starter brush needs to be replaced immediately.

5. Manufacturer's Recommendation

Always check the user manual or recommendations of the motorcycle manufacturer you have. There may be specific guidelines on when to replace the starter brush on the brand's motorcycle.

It is important to remember that replacing the starter brush is a better job done by an experienced technician, if you have no experience in motor repair.

Replacing the starter brush properly can ensure optimal motor performance and prevent further damage to the motor.

The Importance of Brushes on Starter Motors

The starter motor brush is a vital part of a vehicle's starting system. Without a properly functioning brush, the starter motor will not be able to

start the engine
, and the vehicle will struggle or even fail to start.

The brush allows an electric current from the battery to be connected to the rotor of the starter motor, which then generates the initial revolution required to start the vehicle's engine.


Thus, understanding the role of the starter motor brush is key to understanding how the vehicle can be started easily. The better the brush condition on the motor engine, the better the performance of the vehicle starter system.

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