Heaters in refrigerators and freezers are mainly used for defrosting. In No Frost systems, a defrost heater warms the evaporator periodically to melt frost, so air can flow freely and cooling stays stable. Some models also use small heaters around the door frame to reduce condensation and prevent the gasket from freezing.

Common failures include no defrost (heavy ice buildup behind the rear panel, fan rubbing on ice, weak cooling, rising temperature), or overheating during defrost (water leaks, unusual warmth, error codes). Typical causes are a burned-out heater, a faulty defrost sensor/thermostat, wiring/connectors issues, or a control board problem.

Basic steps: unplug the appliance, fully defrost to restore airflow temporarily, then check for recurring ice. Electrical testing and replacement of the heater/sensor should be done by a qualified technician, because it involves mains voltage and internal disassembly.