The system is a pumped CH/HW system, with back boiler and the usual HW cylinder and header tank . When the controller is set at HW "on" and CH "off", the radiators heat up when the boiler comes on to heat the water. It would seem that the motorised valve is stuck in the open position. As these valves are usually spring loaded to close, does this mean I will need to replace the valve, rather than the head. I guess it could also be the controller. Any suggestions of a solution, gratefully accepted.