The a/c in my 2001 s60 won't get cool and upon turning the a/c **** on or off, there is a slight hiss/whistle that goes away after a second or two.

I took the car in and no leak was found and was told to bring it back if the noise started again. The first time I turned the a/c ****, the hiss/whistle occurred.

So I took the car back in and am being told that the condenser needs to be replaced. On top of that, the whistle/hiss that occurs ONLY when the a/c **** is turned on or turned off is being attributed to a faulty oil trap. Does this make any sense? Doesn't this sound more like a compressor issue?

Is the a/c linked to the oil trap in anyway....is it just a coincidence that there are two issues....or am I being scammed? I'm being told that if I do not replace the oil trap that I run the risk of harming the engine and losing the car entirely.

Thanks in advance for any advice!