C/H is OK there is no flow to heating when in DHW mode nor is there backflow down return on heating system the temperature indicated by the control panel varies up and down 35-47c, but on using temperature sensor (infrared remote) on the pipework the readings are incorrect and do not relate to control panel
having problems getting through to you hope my additional information reached you, please "E" mail your answer to question, thanks, Paul
no fault codes on control panel, the fault affects dhw only and not heating which functions OK, in heating mode the firing rate of the boiler seems to regulate up and down as would be expected. The plate heat exchanger is OK as are the dhw & heating return thermistors ( renewed) dhw and cold water flow rates are identical as are the pressures.
I surmise that as there is no affect on the heating flow and return pipes when dhw is drawn, the diverter valve is functioning as per design.The only other thing is the flow meter,the filter is clear, could that partially fail? Thus causing the fluctuating dhw temp