E12 error and the unit reports abnormal temperature or shuts down in cold conditions

Safety: Disconnect power before accessing internal sensors. Avoid working on a frozen unit—allow it to thaw naturally first.

• Locate sensor: On many Cillit models, the temperature sensor is clipped into the valve body or brine line. Refer to the service diagram for exact location.
• Inspect wiring: Check the sensor cable for cuts, abrasions, or pulled connectors. Reseat the plug on the control board.
• Measure resistance: With power off, disconnect the sensor and measure its resistance with a multimeter. Compare to the Cillit temperature/resistance chart. An open circuit or short indicates a failed sensor.
• Replace sensor: If faulty, install a new Cillit NTC temperature sensor, ensuring it is fully inserted into its pocket and secured with the original clip.
• Check environment: Ensure the softener is installed in a frost‑free location within the ambient temperature range specified by Cillit.