99 Camry A/C makes Whistle Sound

Does it do this sound when you have A/C off, but the blower set to maximum ? In other words - try to eliminate problem with a blower motor or something like a leaf/leaves stuck in the vents making this whistle sound... not related to A/C.

If it does the sound only when the A/C is "on" then open the hood while the engine is running with A/C on and try to locate the source of the sound under the hood...

But I bet it is something related with the blower motor... A/C compressor does not run faster when you set it to maximum - it just makes the blower to circulate more air. Speed of the compressor is related to the rpms of the engine, not to the setting of the electric blower motor...

Unless you've definitely pinpointed the source of the sound, have you checked that your windows are all fully closed? I thought I had a problem in my '99 Camry until I exercised the windows full "up." They all looked closed but one of them was the source of the whistling sound. Ditto in my 2006 Tacoma. Good luck.