same problem here,but now it will not ignite on the 2nd stage burn so now no hot water or central heating. have replaced the board,gas valve,air flow switch,set of electrdes and a flame sense electrode. all the work has been carried out by a very experienced engineer and he is now lost as to what it could be. and i am now quite a few pounds ,out of pocket. Please HELP!
Colin Trout, August 2009