Abstract: A power separating apparatus in an automobile comprises first detecting means for generating a first electric signal having a predetermined voltage level when an engine is actuated, second detecting means for generating a second electric signal having a predetermined voltage level when a rotated device is not actuated, determining means for generating a failure signal indicating a failure of the rotated device depending upon a condition of logical product of the first electric signal and the second electric signal when the rotated device should be actuated, and means for controlling an electromagnetic clutch to separate the rotated device from the driving belt on the basis of the failure signal.