F02 displayed and unit does not draw brine during regeneration

Safety: Isolate electrical power and close the bypass or inlet valve before opening the brine system.

Steps to troubleshoot:

• Check brine tank salt level: Ensure there is adequate salt and that a crust or salt bridge has not formed above the water. Break up any bridge with a plastic rod and remove loose chunks.
• Inspect brine line: Follow the flexible brine hose from the brine tank to the Vaillant control head. Look for kinks, pinched sections, or visible leaks. Straighten or replace damaged hose.
• Clean venturi injector: On the control head, locate the injector/venturi housing (often under a small cover held by screws). Remove the injector nozzle and throat, soak them in vinegar or a descaling solution, and gently clean out deposits with a soft brush. Rinse thoroughly.
• Check brine valve and seals: Inspect the brine valve plunger and O‑rings for wear or debris. Replace worn seals or the complete brine valve cartridge if it sticks or fails to seat.
• Test suction: With the unit in brine draw phase (manual regeneration), briefly place the brine hose into a container of water and check for suction. If there is still no suction after cleaning, the internal valve stack or control head may be faulty.

Note: Do not use sharp tools inside the injector or valve seats; scratching surfaces can cause permanent leaks or poor suction.