Display shows “Err 15” and unit indicates high temperature or overheated valve

Safety: Disconnect power. Do not operate the softener if components feel excessively hot.

Steps:

• 1. Check environment: Ensure the Sterling softener is not installed directly next to a water heater flue, boiler, or other heat source. Improve ventilation if necessary.
• 2. Inspect temperature sensor: Locate the thermal sensor on or near the valve body. Check for damage or dislodged mounting.
• 3. Check wiring: Verify the sensor harness is intact and not shorted against metal parts.
• 4. Replace sensor: If the sensor is cracked or readings are obviously incorrect (e.g., error at room temperature), replace the temperature sensor.
• 5. Board evaluation: If a new sensor does not clear Err 15, the main control board may be misreading temperature and should be evaluated by a technician.