I have had this problem for 2 years now and had not really paid mind to it but now it is starting to annoy me. When I turn the a/c on, I get a whistle and when I push the a/c off button the noise goes away. The a/c works perfectly it is just noisy. Any ideas? I have a 99V70 FWD non-turbo.
Thanks

 

Usually that is a bad orifice tube that is bad/torn.

 

Thanks again Tech. Is it going to harm anything if I leave it alone?

 

No not really over a long period of time it will allow small metal shaving to float in the system.