Your problem will be the water flow meter in the machine has jammed and needs replacing. The flow meter rotates and generates electrical pulses to the pcb which counts the pulses to measure the water intake. as it is jammed the pcb now keeps the water flowing too long a second safety switch then drains the water back to the right level and these 2 operate forever filling and draining. The flow meter is a white plastic round device located in the fill hose in the back left corner of the machine. The official Neff description for this component is "Impellor jug" Cheers
Kenjo
January 2014