ZANNUSSI ZX99/5S1?

MY ZANNUSSI FRIDGE/FREEZER MODEL ZX99/5S1 KEEPS ICING UP OVER A 3 WEEK PERIOD THE EVAPORATOR IN THE FREEZER SECTION ICES UP AND THEN STOPS AIR FLOW TO THE FRIDGE SECTION CAUSING HIGH TEMPERATURE, I HAVE CHECKED THE SEALS AND THE MOTOR SEEMS TO BE CONTROLLING, CUTTING IN AND OUT PERIODICALLY AND INITIALLY THE TEMPERATURE IS FINE IS THERE ANYBODY OUT THERE WHO CAN HELP !!