Abstract: A motor controller configured to be coupled to a motor that is coupled to a fan is described. The motor controller includes a processor coupled to a memory, and is configured to operate the motor in a first operating mode in which the motor rotates the fan in a first direction at a first speed. The motor controller is further configured to operate the motor in a restriction detection mode in which the motor rotates the fan in a second direction that is opposite the first direction, determine a torque associated with the motor while the motor is rotating the fan in the second direction, determine that the torque is not within a predefined threshold range in the memory, and determine that a restriction exists in a fluid flow path associated with the motor in response to determining that the torque is not within the predefined threshold range.