this ones baffeled me!!! no heating or hot water until suck on aps tube then only get heating turn hot water on it trips out (lock out) tried new aps/pcb and have linked low pressure switch, over heat switch etc and nothing. then today lockout light was on boiler fired up heating only and went up to 3 bar!!! the other day the boiler fired up with out the fan running and then went to lock out i,m stumped any ideas??? 
