Noisy DISA Valve

NOT the dreaded rattle of a loose flap but a drone like buzzing sound with the engine switched on and it seems to have got louder (or my paranoia is setting in). Anyone experience any increase in noise like that? Do I need to think of replacing?

Norman

Unplug it. If the noise goes then it would be daft not to replace it in case it was an early sign of failure. If the noise is still there with it plugged in then your problem lies elsewhere.