alternator is easy. you just need the right tools. just go through some manuals and figure out how it works. there are even some in the fast nu lab, attached with drill machine.
there is a stator and a rotor. no permanent magnet.
voltage regulator controls voltage to rotor , it energizes the rotor more, as load increases. therefore more current is induced in the stator (electric flux is cut at stator).
but greater the induced current, greater the resisting force (so engine feels the load and slows down).
things to go bad....stator winding, rotor winding, carbon brush, voltage regulator, bearing.
congratulations, you just got the idea of how it works.
to test your wiring, connect one probe to battery negative, other to the alternator positive (jidhar charging wire lagti hai)...if reading is significantly higher, charging wire is bad, or there is bad contact
on a friend's car, blower motor was dying and pulling too many amps