While similar to an actuator, the central locking motor (often referred to as a “gun” or solenoid in aftermarket kits) is the push-pull device that drives the locking rods. In older vehicles or aftermarket installations, this is a separate component added to manual door locks to convert them to power locks. It typically has a rubber boot to protect the shaft from moisture. “Master” motors have 5 wires (to send a signal to other doors), while “Slave” motors have 2 wires (reacting to the signal). Failure usually involves the motor burning out or the rod linkage slipping.