Aircon squealing (not chirping)

[generationgav]

This is on the pre-facelift model if that means anything.

Whenever I have the aircon on (that's a/c illuminated) the car gives off a high pitched squealing sound, it's very hard to describe but it's probably closest to a ac/dc transformer high pitched squealing, but audible even with music on.
This only happens when the a/c is illuminated, and isn't affected by temperature, blowing positions or blow speed.
First of all I want to be 100% sure this isn't normal, and if anybody has seen it before are there any easy/quick fixes? The vehicle is an Elmo one so have told them but not as easy as dropping it into a dealer.

 

[Alb]

Can't say I really notice any noise at all when mine is running.

 

[generationgav]

Can't say I really notice any noise at all when mine is running.

I went out to video the noise so I could demonstrate it - and it's gone, even after a drive. It's an Elmo vehicle so may have been sat not moving for a few weeks/months, I'm hoping that it's just something that has sorted itself out now.