03 suburban a/c belt tensioner

Can someone tell me why my a/c belt tensioner flails violently while accelerating? It's so bad that the tensioner hits the tranny cooling lines that are routed underneath. I replaced the tensioner and yet it still does it and it threw a belt once. If you turn the air on and let it idle for a little bit it doesn't do it. However, sitting in a parking lot with your a/c on and idleing for 5 minutes seems a bit much. I wonder if there's a gm service bulletin on it? If anyone knows if there is a bulletin on it can you give me a bulletin number. Thanks

hello, i have the same problem....my mechanic buddy said i might have to change the ac unit itself(compressor?) it might be the bearing in the clutch that make it sticky? :banghead: its driving me crazy not being able to drive with ac on! its getting hot!. if i get it fixed soon, i can let you know what they say....