Ive just had the same problem on my daughters boiler and the F4 code means condensate trap/pipewok blocked or an ignition problem. check all of your pipework run and if this is clear unscrew the bottom of the condensate trap and clean it. on the side of the trap is a blue plastic cap remove this and make sure that the two screws inside are completely dry. when firing it back up turn the boiler to standby and switch the power back on at the wall. turn the boiler from standby to ch and back again 4 times this resets the ignition sequence. good luck
JAV, December 2010
