HELP!! Sparks shooting off the backside of Alternator

[moparjohn]

Just installed a new (3rd one) alternator.  When your rev. the engine by hand you can see sparks flying from where the wires hook up to the Alt. Cnnection is tight, no exposed wire,  The gauge seems fine. Suggestions please

[chargerman68]

sounds like bad ground

[resq302]

John,

Did you untape the wires and see if the insulation had melted off of them again from the stud loosening up from the last alternator? Just thinking it might be sparking that way.

[Nacho-RT74]

brushes or stud insulation damaged