As above Ben, cracking job as always on that bumper. I think Gary has confirmed my thoughts as to the magnets possibly jamming the motor. Maybe you need to give it 12v off the car and see what it does. I'm a bit concerned you may be over charging your batteries at 14.9v, it should be 14.4 max for lead acid. Have you got the voltage sense wire connected straight to the battery via a fuse or fusible link? I can't remember what was wanted but if you need the pinouts of the alternator I may be able to help if you give me the Denso number.