Whirlpool Refrigerator Error Code OP

The OP error code on a Whirlpool refrigerator indicates that the control board has detected an open circuit condition in one of the thermistor or temperature sensor circuits. A thermistor is a resistive temperature sensor whose resistance changes predictably with temperature. When the control board reads a resistance value lower than the defined COLD limit threshold, it interprets this as an open circuit rather than a valid temperature reading. This typically means the electrical path through the sensor circuit has been broken somewhere between the sensor itself and the control board.

Thermistors in Whirlpool refrigerators are used to monitor compartment temperatures in the fresh food section, freezer section, and sometimes at the evaporator coil. An open circuit in any one of these sensors prevents the board from regulating cooling cycles correctly. The most common causes include a physically disconnected wire harness connector, a broken or corroded wire in the sensor lead, or a failed thermistor where the internal element has cracked or separated. Exposure to moisture, ice buildup around sensor mounting locations, or physical damage during a repair can all contribute to these failures.

Diagnosing the OP code begins with a visual inspection of all thermistor wiring harnesses and connectors, looking for loose connections, corrosion, or visible wire damage. After confirming connections are secure, the thermistor resistance should be measured with a multimeter at a known temperature and compared to the specification for that sensor. A properly functioning thermistor will show a finite resistance value that corresponds to the ambient temperature. A reading of infinite resistance, or open loop, on the multimeter confirms the sensor or its wiring has failed and requires replacement.