Dacor Refrigerator Error Code 99

Error code 99 on a Dacor refrigerator indicates that the control board has detected a shorted thermistor in either the fresh food or freezer compartment. A thermistor is a temperature-sensing resistor whose resistance changes predictably with temperature. When a thermistor short circuits, its resistance drops abnormally low, sending a signal to the control board that mimics an extremely high temperature reading. In response, the system interprets this as a dangerously warm condition, which can trigger compressor and fan overactivity or other protective responses as the refrigerator attempts to compensate for what it believes is a thermal emergency.

Thermistor shorts typically occur when the sensor's internal wiring contacts itself or a grounded surface, often due to physical damage, moisture intrusion, or insulation breakdown from age and heat cycling. The wiring harness connecting the thermistor to the control board can also develop a short if wires are pinched, corroded, or chafed against cabinet edges or refrigerant lines. Because the control board cannot distinguish between a legitimate warm compartment and a faulty sensor producing the same low-resistance signal, the error code is the system's way of flagging the anomaly for diagnosis.

Diagnosis begins at the thermistor connector. Disconnecting the thermistor and measuring resistance with a multimeter will reveal whether the sensor itself is shorted or if the fault lies in the wiring harness. A healthy thermistor will show a predictable resistance value that varies with ambient temperature, while a shorted unit will read near zero ohms. If the harness tests clean but the sensor reads shorted, thermistor replacement is required. Clearing the fault without addressing the underlying short will result in the code returning immediately.