Err18 displayed, unit reports sensor fault related to temperature or internal monitoring

Safety: Disconnect power before opening the control housing.

• 1. Check environment: Ensure the softener is not installed in a location subject to freezing or excessive heat. Correct environmental issues if present.
• 2. Inspect sensor: Locate the internal temperature or monitoring sensor on the control board or valve. Check for broken leads or corrosion.
• 3. Reseat connectors: If the sensor is wired, reseat its connector on the control board.
• 4. Reset control: Power cycle the unit and see if Err18 returns.
• 5. Replace components: Replace the temperature sensor if separate, or the electronic control board if the sensor is integrated and the fault persists.