If you cannot rotate the rotor of a gear motor by hand, what does this indicate?

The statement that the motor is assembled correctly suggests that there are no issues with the internal mechanical integrity of the gear motor being tested. If everything has been put together correctly, there are reasonable expectations for the rotor to be resistant to hand rotation due to the design and intended function of the gear motor.

In many gear motors, especially those that are properly manufactured and assembled, the rotor may not rotate freely by hand due to design aspects such as tight tolerances or the presence of gears that require sufficient torque to overcome inertia and overcome friction. Therefore, not being able to turn the rotor manually does not necessarily indicate a problem; it may be an expected characteristic of the gear motor's functionality, especially if it has yet to be energized.

By contrast, if there were issues such as contamination, improper clearances, or incorrect bearing sizes, these problems typically would lead to an unusual resistance or binding that would indicate a malfunction within the assembly. The absence of these symptoms supports the idea that the gear motor is functioning as designed when it cannot be manually rotated.