Under the water bottle is a drain hole,when the bottle overflows water runs down this hole through a pipe to a reservoir behind the condensor unit, there is a float in this reservoir that rises and clicks a switch that activates the full tank light and stops the machine working,
removing the stopper at the rear and emptying the reservior should do the trick,If the float does not go back down due to dirt in the machine the left hand side panel can be removed by taking off the top then the retaining screws,one inside at the top the rest in the back panel,remove the one screw holding the float switch unit and clean the black float.(Make sure it's not plugged in)
Bob, January 2008