Fridge not working ,took off back of freezer compartment, fan working inside,evaporator iced up,there are two flat black sensors on the same pipe,white sensor on pipe out of coil,sensor on polysterine on front of evaporator,two wires which dissapear into coil,heaters? which of these are faulty and are they easy to replace? any help would be gratefully received

GARRY1541, January 2009