92 960 Wagon,177,000, converted from R12 to R134(?), from old freon to new stuff a couple of years ago. I run A/C all the time. Recently, at idle I notice that I'll hear a growl from the A/C circuit like a bearing or tensioner is going bad. If I hit the "A/C off" button the noise immediately disappears like some "clutch" has been disengaged. Unfortunately I don't know clutches from compressors so some of the previous posts and search function are only of marginal use to me. Any help would be greatly appreciated. Thanks.