What is a common reason that could cause a starter motor not to engage?

A starter motor not engaging can often be attributed to a failure within the starter motor itself. This could manifest as issues such as worn brushes, a defective solenoid, or internal damage due to overheating. Whenever the ignition key is turned, a functional starter motor should receive power from the battery and activate the solenoid, which engages the motor to crank the engine. However, if any components within the starter motor are faulty or have reached the end of their lifespan, the motor will fail to operate.

Battery voltage checks and alternator output checks are important diagnostic tools, but they focus on other aspects of the vehicle's electrical system. The ignition switch plays a crucial role in providing power to the starter motor; however, if the starter itself is defective, it won't engage regardless of the condition of the ignition switch or the battery voltage. Understanding the mechanics of how the starter motor functions is essential for accurately diagnosing the issue when it fails to engage.