help and advice needed please,changed the flow switch assembly(complete)on this boiler yesterday all ok on leaving,however customer rang back today boiler wont switch off even when the clock/programmer is off,went back to it and indeed it would'nt shut down.got the burner to shut off briefly by turning the stat down to 1 but the pump kept running till the burners came in again,seems ok in water only mode will start up and shutdown ok prob only when in htng mode,checked microswitches(the ones i could get to,they were ok,isolated clock- burners still lit up though......any please.