As Dave mentioned check for voltage at the wires that plug into the motor. You have three power wires; red, yellow and green. You should have voltage at the green wire in either direction. You will have voltage at the red wire in one direction and the yellow wire in the other direction. If that's good then check that the black wire in the harness is grounded to the body of the car with an ohmmeter or test light. If that's good then it has to be the motor. If you don't have a good ground then the circuit breaker is bad or not grounded. Connect a wire directly from the black ground wire coming from the motor to the body and see if it works.