Sure sounds like something is wired backwards but wiring the sensor backward will not make the motor run backwards. Somewhere, somehow the polarity on that motor is reversed. The signal generated by the sensor is a simple ac waveform, if the wires were reversed it would cause the signal to go up before it went down or vice versa. The only thing it needs to do is send out frequency, the more up and down lines in a given time period equate to more or less miles per hour, that speedo head could give a shit if the ac wave starts neg or poss, just the frequency at which it operates.

Mark