Was there a slip of paper in the box with the regulator? Should have been, showing you to "polarize" it with the generator for positive or negative ground, after mounting it.
57 GMC LCF 370 55 John Deere 40-W 59 John Deere 430-W 2000 GMC 4x4 56 John Deere 420-W Pix on Photobucket
