What does it mean when the key makes a clicking sound but the engine won't start?

[MacJulian]

The reason why the key makes a clicking sound but the engine won't start is due to a malfunction in the starter. Common faults include: the starter not turning or moving slowly, loose terminal connections, severe wear of the brushes, short circuits or open circuits in the field coil or armature coil, dirty commutator, or protruding mica sheets causing poor contact between the brushes and the commutator. The solution is: use a household multimeter to measure whether the car battery voltage reaches 12V or above. If the measured voltage is less than 10V, the vehicle cannot be started, and the battery must be charged or jump-started using another vehicle's battery. If the battery is normal, use the multimeter to check if there is power at the starter's power supply terminal. If there is no power, it indicates a power supply issue in the starting system, and it is necessary to check for loose, broken, or aged starter wiring. After repairing, try turning the key to start the engine again.