Refrigerator displays EC50; temperatures may be erratic or not matching the setpoint.

Safety first: Disconnect power before accessing control boards or sensor wiring. Avoid static discharge when handling electronic parts.

Step 1 – Confirm temperature issues

• Use an accurate refrigerator thermometer to compare actual compartment temperature to the setpoint.
• If readings are far off or fluctuate widely, a faulty thermistor may be misreporting temperature.

Step 2 – Locate the thermistor

• Most Sub‑Zero models have thermistors behind small plastic covers on the interior walls or near the evaporator.
• Remove the cover to expose the sensor bulb and wiring.

Step 3 – Test thermistor resistance

• With power off, disconnect the thermistor from the harness.
• Measure resistance with a multimeter and compare to Sub‑Zero’s temperature‑resistance chart (for example, around 10kΩ at 77°F, depending on model).
• If the reading is open, shorted, or far outside expected range, replace the thermistor.

Step 4 – Inspect wiring and connectors

• Check for pinched, broken, or corroded wires between the thermistor and the main control board.
• Reseat connectors at both ends to ensure a solid connection.

Step 5 – Replace thermistor if faulty

• Install the new OEM Sub‑Zero thermistor in the same location and routing as the original.
• Secure the sensor and reinstall any covers.

When to call a professional: If thermistor readings are correct but EC50 persists, the main control board’s sensor input may be defective and should be evaluated by a Sub‑Zero technician.