My boiler is 8 years old. For as many years as i can remember it has had a lockout problem intermitantly. I had a new board after one episode. Now it doing it again. It appears to stem from the air pressure switch. When it is fixed to its holding plate in a vertical position the boiler goes to lockout. When i remove the switch from its holding mount and let it hang loose , everything works ok. If i gently turn it over i hear the switch click and lockout happens again.I see no sign of damaged wires or tubes. The boiler is operating ok now, but i have to have the outer casing off and the switch hanging in a flatish position. Gas engineer is baffled. For some time i thought it might be the wind. Fan is operating ok when air switch is hanging loose on its connections.Today i replaced the air switch with another one, result was the same. I am thinking of a new boiler, but dont want to be beaten by this baffling fault. Any ideas please.