Toshiba satelite c660 sudden shutdown

how to change c660 microphone and main problem is how to fix.........sudden shutdown...after charge finished....even though it connected to charger

if the laptop is fully charged it will not shutdown..it work fine ...but if the charge is finished and I plug in charger.it shows charging but it will not charge and suddenly shuts down after 2 to 9 min...and it will not charge within 2 or 3 days and again same thing if it is fully charge.......same story........pls need help........