charging system blues

here now with car - pulled green field off alt , grounded spade on alt housing saw the little spark but no volt increase across battery listened for it to draw when field grounded & got none. black wire back of alt is hot with key off - good volt readings at key points - think its safe to say i have a bad alt - gets a reg too . how'd i do ? ammeter in dash fooled me- shows chg with a bad alt. thanks . mike