Have any of you noticed a "clicking", "phtting", "flapping" or any other kind of strange noise coming from the air con unit when its turned on and your travelling at 40mph+

Its definately the unit because when I turn it off, the noise disappears

I've mentioned a loud click from the unit when it is initially turned on and they say it is a normal noise - I personally think its a tad loud to be honest. The unit isn't as refined as I'd hoped it would be - am I expecting too much from a Ford Fiesta?