to help anyone i have had a fridge warm fault on my zanussi for weeks, it all started when we accidently left freezer door slightly open. the fridge started to get warm, defrosted all ok for a while but fault returned. checked forums told to lower evaporator in freezer and defrost, test evaporator heater for open circuit (connections behind panel in freezer) and compare both sensors, resistance monitored to see if they responded to cold (used bag of frozen peas) checked but fault still same.
called engineer he said that the defrosting of the snow like frost on evaporator, does not defrost the ice that that has formed in the defrost drain pipes due to us leaving the door open this needs 72 hours. defrosted has told, all ok.