L298 IC motor driver - how to wire and use correctly?
You show a 3v supply to VCC, that's ok but the 5 volt regulator on board will not be doing anything, the 5volt reg supplies the logic supply.
Am I to assume you have supplied this separately, it looks like that from your diagram.
Try connecting 6 volts to VCC, disconnect the 5volt supply (if there is one) now try, use a resistor across the output of say 100ohms.