Norcold Refrigerator Error Code Thermistor Fault (flashing COLD snowflake)

The flashing COLD snowflake on a Norcold refrigerator indicates a thermistor fault condition. The fin thermistor is a temperature-sensing resistor mounted on the evaporator fins inside the cooling unit compartment. The electronic control board continuously monitors this thermistor's resistance to track fin temperature and regulate cooling cycles. When the board detects that the thermistor circuit is either open (infinite resistance, indicating a broken wire or failed sensor) or shorted (near-zero resistance, indicating a wiring short or sensor failure), it flags the fault and triggers the flashing snowflake display. This fault can appear regardless of which operating mode the refrigerator is running in: AC, DC, or gas.

When this fault is active, the control board does not simply shut down. Instead, it switches to BOS (Backup Operating System) mode, which runs the refrigerator on a fixed duty cycle rather than relying on real-time temperature data from the fin thermistor. This means the refrigerator continues to operate, but without precise temperature regulation. Cooling performance may be inconsistent, and the unit may over-cool or under-cool depending on ambient conditions. The BOS mode is a protective fallback, not a long-term operating solution.

The most common root causes involve the lamp-thermistor wire assembly, which combines the interior lamp wiring and the thermistor sensor into a single harness. This assembly is subject to physical damage from door contact, moisture intrusion, and connector corrosion. A healthy fin thermistor will read a predictable resistance value at a given temperature, and measuring it with a multimeter is the primary way to determine whether the sensor itself has failed or whether the fault is caused by a wiring or connector issue.