Sub-Zero Error Code 10 r 00: Refrigerator Evaporator Thermistor Open

Sub-Zero code 10 r 00 on a Built-In (BI) unit means the control board is seeing an open circuit from the refrigerator evaporator thermistor (temperature sensor). In plain terms, the board can no longer read the temperature at the fresh-food evaporator coil, so it cannot manage cooling and defrost correctly. Diagnosis involves measuring the thermistor's resistance (Ohms) and comparing it against the expected value at a known temperature.

This is a diagnostic-grade fault that requires a multimeter and the correct Sub-Zero resistance chart. If you are comfortable doing only owner-safe checks, the right move is to note the code and have a qualified technician verify the thermistor reading before any part is replaced.

The meaning of 10 r 00

The evaporator thermistor is a small temperature sensor mounted on or near the refrigerator evaporator coil. It changes resistance as temperature changes, and the control board uses that resistance to decide when to run the compressor and when to enter defrost. An "open" reading means the circuit is broken: infinite or out-of-range resistance, typically caused by a failed sensor, a broken wire, or a disconnected plug. The correct verification is to measure Ohms at the thermistor and confirm the value matches the expected reading for the measured temperature.

Most-likely causes

• Failed evaporator thermistor (internal element open)
• Broken, pinched, or corroded wire in the thermistor harness
• Loose or disconnected thermistor connector at the sensor or control board
• Moisture, ice, or condensation intrusion at the connector causing an intermittent open
• Control board input fault misreading an otherwise good sensor (less common)

Safe owner checks

• Power cycle the unit: turn it off at the panel or breaker for about 5 minutes, then restore power and see if the code clears.
• Visually check that nothing has snagged or pulled on interior wiring during recent loading or cleaning.
• Make sure the unit has not been recently iced over from a door left ajar, which can stress sensor connections.
• Note when the code appears (constantly vs. intermittently) so the technician can target the diagnosis.

When professional service is needed

Confirming an open thermistor requires measuring resistance with a multimeter, comparing it to the Sub-Zero Ohms-vs-temperature chart, and tracing the harness back to the control board. Replacing the sensor, repairing the harness, or replacing the board involves disassembly inside the cabinet and proper reassembly. A technician should verify the reading before any part is swapped to avoid an unnecessary control-board replacement.