Electrolux Microwave Error Code E-21

The E-21 error code on an Electrolux microwave indicates an open circuit condition in the thermal sensor. The thermal sensor is a temperature-monitoring component responsible for measuring heat levels within the microwave cavity or on critical components such as the magnetron. When the control board sends a signal to poll this sensor and receives no return signal or a circuit reading that indicates infinite resistance (open), it triggers the E-21 fault and typically halts microwave operation to prevent damage from undetected overheating.

An open circuit in the thermal sensor means the electrical path through the sensor has been broken. This can occur because the sensor element itself has failed internally, which is common after prolonged use or exposure to excessive heat. The sensor may also test open if the wiring harness connecting it to the control board has developed a break, or if a connector has corroded or pulled loose from its terminal. Since thermal sensors rely on a continuous and measurable resistance path, any interruption in that path will register as an open fault.

Diagnosing E-21 begins with physically inspecting the thermal sensor and its wiring for visible damage, then using a multimeter to test continuity across the sensor terminals. A properly functioning thermal sensor should show a measurable resistance value at room temperature. A reading of infinite resistance (OL on a digital multimeter) confirms an open sensor that requires replacement. Check all connector terminals for corrosion or looseness before condemning the sensor itself.