98 A/C comp knocking

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Greetings All,
My wifes 98 Century 3.1 has developed a noise that sounds like a piston rod knocking but it is in the A/C compressor. The A/C still blows very cold. It has a variable displacement type compressor which I am unfamiliar with. I have read that this could be caused by air in the system. I do not see how air could get in. Is there any way to tell whether a vacuum down and recharge would be worth it or is this compressor a lost cause? Here in Florida the A/C shops ALWAYS say you need a new comp. This one is not cheap(several hundred dollars at autozone). It would not be hard to replace, just expensive.

I removed the fuse for now to prevent further damage to the car, but my wife is going to kill me.