Whirlpool Microwave Error Code E3

The E3 error code on a Whirlpool microwave indicates that the temperature sensor circuit has developed a short condition. The temperature sensor, sometimes called a cavity thermistor, is a resistive component that monitors the internal cooking cavity temperature and provides feedback to the control board. Under normal operating conditions, this sensor has a resistance of approximately 1080 ohms at 70 degrees Fahrenheit, increasing by roughly 2 ohms for every additional degree of temperature. When the control board detects a resistance value that falls outside the valid range for a short condition, it triggers the E3 fault and typically halts microwave operation to prevent damage or unsafe conditions.

A shorted sensor means the resistance has dropped abnormally low, below what the temperature curve allows. This can result from a failed sensor component itself, damage to the sensor wiring harness, or a connector that has been exposed to moisture or grease over time. The sensor is a sealed unit mounted inside the microwave cavity or within the cavity wall, and its two-wire connection runs back to the main control board. Damage along this wiring path, such as pinched or melted insulation creating a short to ground or between wires, can produce the same fault as a failed sensor.

Diagnosis begins by disconnecting the sensor and measuring its resistance with a multimeter. At room temperature around 70 degrees Fahrenheit, a reading close to 1080 ohms confirms the sensor is functioning. A reading near zero or dramatically below the expected value confirms a short. If the sensor itself measures correctly, inspect the wiring harness for visible damage, and check connector pins for corrosion or contact bridging before replacing any components.