Most basic rotators have a 24 volt AC that runs the AC drive motor. Any other component on those lines will stop the motor. You can measure the voltage trying to turn the rotator with any AC volt meter. as mentioned above.
( this is a motor start capacitor.)
There is almost always a 'limit switch' . if those fail, nothing runs.
More advanced rotators may have a drive IC with feedback. If that fails, nothing turns.
This feedback may even indicate position.
More advanced yet (digital) use a stepper motor/ drive IC, and the feedback tells a microcontroler what is up.
Anything fails there, nothing works. (usually a fail indicator here)
Look up basic remote servo circuits for a better understanding.
antenna rotor wiring diagram - Wiring Diagram (2bitboer.com)
I built a positioner for a small dish using a heavy duty pan and tilt mount for a camera. Both azimuth and elevation.
The controller all digital, computerized. Tracking things like orbiting satellite/ ISS and such.
I could use 'WXtrack to run it. The plans were found on QRZ website, I just modified it heavily.
(IE
Antenna Rotator Controller (kg4jjh.com)
anyway, you get the idea.