welder107257

Hi ive got a worcester bosch highflow 400 rsf,just had worcester bosch out 2 months ago and they fitted a new DHW heatexchanger,new pump and serviced it ,its been working great until i switch the CH on for about 1 hour , but now it will not pump out hot water even when i turn CH switch of and room stat off its heating the rads on the HW side,ive tested at the diverter valve and it is energising e.g small screw driver sticks to it any ideas,many thanks Dave.ps the green demand light is not on when rads are heating up on DHW.