Vaillant Diverter Valve Passing / Stuck Mid-Position

Radiators get hot when only hot water is requested on a Vaillant combi

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Worn diverter valve seals, Sticking diverter valve spindle, Faulty diverter motor head, Debris in hydraulic block

Safety: Pipework may be hot; take care when touching near the boiler.

Confirm symptom: Run a hot tap and feel the flow and heating flow pipes under the boiler. If both get hot, the diverter is passing.
Cycle heating/hot water: Turn heating on and off a few times to see if the valve frees temporarily.
Engineer repair: Diverter valves are internal hydraulic components. A technician can replace the cartridge or complete valve assembly and flush debris from the system.

Hard 4/5

Diverter Valve Assembly

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