A method for detecting blockages of unipolar stepper motors by analyzing the motor current supply, comprising impressing a current into one or more motor windings using a controllable switch, wherein the switch selectively connects a respective motor winding connection to a supply voltage connection and wherein the connections of each motor winding lying at a common potential are permanently connected to a second supply voltage connection, wherein a current feed variant has phases between the switching of the motor windings, in which phases the motor winding connections are switched with high resistance; detecting the voltage at a motor winding connection at least for the high-resistance phase and comparing the voltage to a threshold; detecting a time interval for which the voltage is greater than the threshold; comparing interval lengths for several motor winding connections, and detecting a blockage based on the comparisons of interval lengths.