Daewoo Microwave Error Code ERROR 3

ERROR 3 on a Daewoo microwave indicates a thermistor fault or heater failure detected during convection or grill operation. The thermistor is a temperature-sensing resistor that monitors cavity heat during cooking cycles. The control board reads the thermistor's resistance continuously, and when that reading falls to 0 ohms (a short circuit) or rises to infinite resistance (an open circuit), it triggers ERROR 3 and halts operation. At room temperature, a healthy thermistor should measure approximately 100K to 1000K ohms. Any reading outside this range signals that the sensor has failed and the board can no longer trust temperature feedback.

If the thermistor checks out within spec, the fault source shifts to the heater elements themselves. Daewoo convection microwaves typically include multiple heaters, such as a convection heater, an upper grill heater, and a lower heater. Each of these elements must show continuity when tested with a multimeter. A break in continuity anywhere in a heater circuit means the element has burned out internally and is no longer capable of producing heat. The control board interprets a missing heater circuit as a critical failure and throws ERROR 3 to prevent unsafe or incomplete cooking cycles.

Common root causes include thermistor degradation from prolonged high-heat exposure, physical damage to sensor wiring, or heater element burnout from repeated use or power surges. Because this error involves both sensing and heating components, a systematic approach is required: test the thermistor resistance first, then move to continuity checks on each individual heater. Skipping the thermistor check and replacing heaters blindly is a common and costly mistake, since a failed thermistor costs far less to replace than a full heater element.