Did the car have A/C that was removed? You're either missing the ground or the motor is bad....that's my guess anyway. The easiest way to isolate the problem is to pull the inner wheel well, measure for 12 volt at the motor connector. If you've got 12 volt there, try a jumper from the motor housing to ground to see if it works. If it does, run a new ground wire. If it doesn't, replace the motor.