Whining air con
 

I've just been out food shopping and had my air con set to 18. There was a very high pitched whine, almost a whistle coming through that was actually drowning out the radio. It is only a 5 minute drive so I don't know if it disappears after a while.

Has anyone else experienced this, or has any idea what might be causing it? Thanks.

It sometimes happens when there is much air circulation and one of the center vents "leaks" a bit.
If that is the cause, opening the vents solves it.