A thermistor failure is a broad code indicating that a temperature-sensing thermistor has stopped providing reliable data. Unlike the specific open or short circuit codes, this fault may indicate a drifted sensor — one that still produces a reading but one that is inaccurate enough to trigger the fault threshold.
What Triggers This Error?
The board may detect readings that are physically inconsistent — for example, a freezer sensor reporting 40°C when the evaporator coil is clearly frosted — suggesting the sensor is alive but reading incorrectly.
Common Sources
- Sensor drift with age: All thermistors drift slightly over years of use. Most refrigerators can tolerate minor drift, but significant deviation triggers a fault.
- Partial wire damage: A partially broken wire creates intermittent high resistance, causing erratic readings.
- Heat damage to the thermistor: Thermistors mounted near defrost heaters can be physically damaged by direct heat contact.
- Contamination: Grease, cleaning agents, or food residue on the sensor element affects its thermal response.
Solutions
- Cross-check with a separate thermometer: Place a calibrated thermometer in the compartment and compare readings to the displayed temperature. A significant discrepancy points to a drifted sensor.
- Inspect sensor mounting: Ensure the thermistor is correctly clipped into its mounting bracket and making proper thermal contact with the measurement surface.
- Clean the sensor: Gently wipe the sensor element with isopropyl alcohol to remove any contamination.
- Replace the thermistor: A drifted or heat-damaged thermistor cannot be recalibrated in the field. Replacement is the correct resolution.