Whirlpool Defrost Thermostat (W10225581)

The Whirlpool Defrost Thermostat monitors evaporator temperature during the defrost cycle and helps control when the defrost heater turns on and off. It closes when the evaporator is cold so the heater can run, then opens as the coil warms to stop the heater and prevent overheating. Failure is often caused by normal wear, moisture intrusion, corrosion at the contacts, or a weakened internal bimetal that no longer opens or closes at the right temperature. Wiring or terminal damage can also cause intermittent operation. These symptoms can help you decide if the Whirlpool Defrost Thermostat matches your issue: Frost or ice builds up on the freezer back wall or on the evaporator coils Freezer gets warmer over time even though the compressor runs often Fresh food section warms because airflow from the freezer is restricted Defrost heater does not come on during defrost, leading to heavy frost Defrost heater stays on too long, causing overheating, melting, or burnt smells Temperature swings that improve briefly after unplugging or manual defrosting