1994 Jeep Grand Cherokee Air conditioning compressor/clutch

Hello,
I own a 1994 jeep grand cherokee Laredo and haven't had too many problems with it. However, this past winter I noticed a metal on metal grinding/zipping noise only for a quick second when first starting the vehicle and only after it had been sitting all night in cold weather. It would not make the noise when driving, only when first turning the key over. Now that summer is here and I am running my air conditioner, the problem has became much worse. Now it makes the same noise every time I start the vehicle and also any time I turn the air conditioner on. If I do not turn the a/c on it does fine. However, as soon as I turn the a/c button on it makes the grinding noise constantly (worse when first driving and accelerating/turning. It also has started squealing really bad and the power steering will lock up occasionally when the air is on as well. We changed the serpentine belt and the fan clutch, but it has not solved the problem. We are hoping to avoid having to change the entire compressor, thinking it is possibly the compressor clutch? Thank you for any assistance you can offer.