F07 error and the display shows abnormal temperature or freezes during regeneration

Safety: Isolate power before opening the control housing.

Actions:

• Check ambient conditions: Confirm that the softener is not installed next to a boiler flue, radiator, or in direct sunlight. Vaillant softeners typically require an ambient temperature within the range specified in the manual.
• Improve ventilation: Ensure that the control head vents are not blocked by insulation, boxes, or other equipment. Provide at least the minimum clearance recommended by Vaillant.
• Inspect for moisture: Look for signs of condensation or water ingress inside the control housing. Dry carefully and identify any leaks from plumbing connections above the unit.
• Check temperature sensor: Some boards have a small thermistor near the power components. Verify that it is firmly attached and not physically damaged. If the sensor is replaceable, fit a new one of the correct value.
• Reset and test: After addressing environmental issues, restore power and clear the F07 code. Monitor the unit during a full regeneration to ensure the error does not recur.

Warning: Persistent F07 errors may indicate failing power components on the PCB, which should only be serviced by an authorised Vaillant technician.