Wondering if any members have come across a condenser fan controller on a Williams Freezer Walk In Room outdoor unit.

I say "controller" because Im not sure its a fan speed controller, which rather modifies the speed of the fan motor.

This controller cuts the power to the fan when the temperature of the coil reaches certain limits.

My question is, how does it work? and whats it supposed to do.
The marking on the controller has a knob which can be turned between 30 c and 60 c.

controller has a probe/sensor which is located at the bottom of the condenser coil.

Are these units prone to failure?
How do I test it? Or should I just replace?

Thank you