Boiler fires up fo 30 or so seconds, the pump runs and the system seems to be working then the boiler stops and the pump still runs and the circulation of water/central heating not workin. I have chnaged the 3 port vavle and motorised valve but still no working correctly

John, May 2009

your pump sounds like it is working , it is not ,check the vent screw to see that the pump is spinning,new pump

stew, May 2009

sounds like theres a blockage

b, May 2009