A/C Whistle

[Snap-on]

Alrighty,
I got my air con on the vp converted fron r12 to r134a the other day. Ever since it has had an annoying whistle/squeal/high pitiched noise coming from the air vents. This is only heard inside the car. And only comes on when the compressor is engaged and the motor is at about 2000rpm or higher.

Any one else had this problem/know what it is? Any help will be much appreciated.

[DERTY]

Mine also does this.

[Sharpie]

Mine too. Spoke to an a/c bloke today and he reckons its under charged.