Display shows F14 and unit indicates sensor temperature error

Safety first: Disconnect power before accessing internal electronics. Do not open any pressurized water connections.

• Locate temperature sensor: On some Viessmann softeners, a temperature sensor monitors inlet water temperature. Find it on the inlet manifold or valve head.
• Check connection: Ensure the sensor plug is firmly connected to the control board and that the cable is not damaged.
• Inspect mounting: If the sensor is inserted into a dry well, confirm it is fully seated and has good thermal contact.
• Reset and test: Restore power and clear the F14 error. Monitor the displayed temperature for stability and plausibility.
• Replace sensor: If the reading is erratic or F14 returns, replace the Viessmann temperature sensor. If the new sensor does not resolve the issue, the control board may be defective.