Sounds like the armature is gone. Instead of repairing spend your money on a new 19.2 volt Craftsman.
I am in the construction business and use cordless tools almost daily. Replaced all of my DeWalt tools with the Craftsman several years ago and have never regretted the transition.
Only failure I have exprienced is with an impact driver after about five years of heavy use. Dollar for dollar the Craftsman are hard to beat. JMO.
Ken