A stepping motor is a small electric motor that converts digital pulses into mechanical rotations. Every revolution of the motor is a small, discrete step controlled by a digital pulse. Each step is the same size and requires a separate pulse. As the pulses increase in frequency, the stepping motor exhibits continuous rotation, although it's actually making discrete revolutions very quickly. The motor consist of two inductor windings; one winding is responsible for clockwise rotation and the other for counterclockwise rotation. Stepping motors are used in industrial applications in which digital signals must be converted or translated into mechanical motion.

Determine the type of stepping motor you have: bipolar or unipolar. A bipolar motor has four leads while a unipolar has six.

Determine the resistance of the windings. Each stepping motor has two windings; use an ohmmeter to test each winding by connecting the ohmmeter to the input terminals of each. If you have a bipolar motor, place the ohmmeter between the positive and negative input terminals of each winding. The resistance of the two windings should be exactly the same. If not, the motor must be replaced. If you have a unipolar motor, place the ohmmeter between the positive terminal and the com terminal and then between the negative and com terminals. Do this for each winding. In each case, the resistance should be the same for all measurements; if not, the motor must be replaced.

Connect a 9-volt battery to the motor and step the motor through its various rational positions. Since each stepping motor is different, refer to the specifications for your stepping motor to know how your motor should respond when you place the battery on any combination of terminals. For example, the leads on a stepping motor are color coded; red, yellow, black and orange, for example. If you power the red and black terminals with 9 volts and leave yellow and orange at 0 volts, it may translate into a clockwise rotation of the motor (or whatever is specified in your stepping motor's specification for that combination). If the motor responds according to the specification, you have a good motor; if not, replace the motor.