97 LS -noisy A/C Compressor

Hey just got the a/c system filled with a little over 2lbs of gas for the a/c. My mechanic said the noise at startup was from the compressor. So when I switch the a/c on (bi-level, or norm) the noise goes away. However if I just turn the ac off (to vent ) the noise comes back.

What is the cause of this A/C Compressor noise? How can it go away?

Thanks for your ideas+comments!

97 Buick Regal LS 187kms

It is a bearing gone bad in the a/c pump.

Mine does the same thing. ie:

the noise stops after I turn on the A/C.

There are 2 types of compressors in the Buick's.

1 of them you don't need to purge the tank.

I can post the how to on Monday if you like.

Cheers
Stripe

Could be the clutch starting to go mine was doing that on a '96 regal it finally went though and broke my serpentine belt..put a bypass pulley in...check to see if its the clutch

thanks for both replies to this issue...I've had the serpentine belt replaced, I will find out about the noisy clutch and follow up if it needs to be replaced. Or I will just live with the noise if its too much $$$ lol

thanks