Freezer not freezing — Madrid, Madrid

When a freezer stops maintaining temperature below 0 °F (−18 °C), food begins to thaw and spoil — often silently, since modern freezers don't always alarm until the temperature rises well above the safe zone. In a top-freezer or side-by-side refrigerator, the freezer compartment shares a sealed refrigerant system with the fridge section, and the most frequent cause of a warm freezer is frosted-over evaporator coils behind the rear panel. When the automatic defrost system fails — typically a burned-out defrost heater, a stuck defrost timer, or a faulty defrost thermostat — frost builds on the evaporator until airflow through the coils is almost completely blocked, leaving the freezer warm while the fridge side may also climb. Other causes include a failed evaporator fan motor (the fan that circulates cold air from the evaporator through the freezer compartment), a malfunctioning compressor or compressor start relay, a sealed-system refrigerant leak, or a defective temperature control board. In stand-alone chest or upright freezers, worn or torn door gaskets are a common culprit: the warm, humid air that leaks in overwhelms the cooling system and accelerates frost buildup. Diagnosis involves checking compressor operation (is it running? cycling?), testing the evaporator fan and defrost components for continuity, measuring the temperature at the evaporator coil inlet versus outlet, and inspecting door seals with a dollar-bill test (close the door on a bill — if it slides out easily, the gasket isn't sealing). An appliance repair technician can replace the defrost heater or thermostat, swap the evaporator fan motor, or diagnose sealed-system issues that require a licensed refrigeration technician for refrigerant recovery and recharge.