It`s the pump and float at the back of the machine,if you look at the bottom on the right hand side, you will see a grey oblong plastic unit this houses the pump and float valve.if the chamber is full of water it activates the float valve and cuts off the thermostat.
To check prise the 2 lugs that clip it to the machine back, ease top cover apart if there is excess water in there,your pump`s knackered.Pump and float valve kit about £30 from Indesit spares,remember the switch off the electric first.
Stevie T, September 2010