how can i stop the fridge part of fridge freezer freezing up?

I have a Hoover A class frost free fridge freezer (freezer at bottom and fridge at top)...I pulled the freezer forward and found plastic tray full of water so i emptied it thinking this would cure problem of fridge part freezing up but it's still freezing up ...the fast freeze or "super" light starts flashing sometimes also...i don't know how fridges are supposed to work so should there be some water in the moulded tray at the bottom of the tube coming out of the back of the fridge or not ?...
Thanks Brian