Vaillant smart thermostat shows F.07 and cannot control the heating zone valve; selected zone does not heat.

Safety: This involves mains voltage to actuators/valves. Isolate the heating system at the main switch and verify power is off before working.

• 1. Identify the affected zone: Use the thermostat’s zone menu to see which zone reports F.07. Locate the corresponding actuator or motorised valve near the manifold or pipework.
• 2. Check wiring connections: At the wiring center or thermostat base, ensure the zone output wires are secure. Look for signs of overheating or melted insulation.
• 3. Test actuator operation: With power restored briefly, call for heat on that zone and listen/feel for the actuator moving. If it does not move and F.07 appears, power off again and test the actuator separately according to its datasheet.
• 4. Inspect for shorts: Use a multimeter to check resistance of the actuator coil. A very low resistance may indicate a shorted coil that can damage the thermostat output.
• 5. Replace faulty actuator: If the actuator is jammed or electrically faulty, replace it with a compatible Vaillant or approved actuator.
• 6. Replace controller output if needed: If a known‑good actuator still does not operate and F.07 persists, the thermostat or wiring center relay output may be damaged and should be replaced by a professional.