Sub-Zero Refrigerator Error Code 20 2 06

Error code 20 2 06 on a Sub-Zero refrigerator indicates a defrost bi-metal miswire condition combined with overheating during the defrost cycle. The bi-metal thermostat is a thermal cutout device mounted directly on the evaporator or defrost heater assembly. Its job is to interrupt power to the defrost heater once the evaporator reaches a safe upper temperature limit, typically in the range of 40 to 60 degrees Celsius depending on the specific model. When the control board detects that temperatures during defrost have climbed to abnormally high levels and the bi-metal has not responded as expected to cut power, it logs this fault code.

The most likely root cause is a wiring error at the bi-metal connector, which can result from a previous service where wires were reconnected incorrectly, or from damaged wiring that has caused a short or open circuit in the bi-metal loop. If the bi-metal is wired out of the circuit entirely, the defrost heater will run unchecked, producing dangerously high temperatures. Alternatively, the bi-metal itself may be physically improperly mounted, meaning poor contact with the evaporator surface, which prevents it from accurately sensing temperature and tripping at the correct threshold.

A secondary but less common cause is a bi-metal that has failed in the closed position, meaning it never opens even when temperatures exceed its rated limit. In this case the heater runs without interruption, and the control board detects the thermal anomaly through its own sensors. Diagnosis begins with a careful inspection of the bi-metal wiring connections and physical mounting position before condemning the bi-metal component itself.