Method of detecting an error in an actuating device

At least one operating device is arranged along the transmission link between the clutch and an actuator. The maximum movable path between an end point near the actuator and an end region near the clutch is stored in memory and compared with the distance measured in operation to detect an error. The operating device may be a hydraulic disengaging system. Independent claims are also included for a hydraulic operating device, and for a further method of detecting errors.