Help! Can't pinpoint squeal from belt drive.

[akram]

This is on a 2007 Silverado 2500 HD Classis, 6.0, 4x, 100K. As a preventative measure I decided to replace both tensioner pulleys and idler pulley as I thought they were getting a little noisy. I order the parts from GMpartsdirect.com. I also got a new AC belt. Well after putting on the new pulleys I've got a nice squeal going on. First I thought it was the alternator, replaced that, nope didn't cure it. Next fan clutch, nope didn't cure it. The only thing left is the AC compressor and water pump. I've tried countless times to diagnose and listen where the noise is coming from hence my attempts at solving the issue. The noise is present at low RPM's with light throttle. My question is why did this noise appear after replacing the idlers and belt? And second do I go ahead and replace the compressor or can I do just the bearing? I read a post here where they did just the bearing.

[Dnt]

Incorrect belt. There are 2 different belts one is slightly too long and the parts place gave you the wrong one. Happens all the time it is dependent upon the alternator size that the truck has just go trade the belt before you bankrupt yourself trading out other parts..

[akram]

The belt wasn't the issue for me, the parts store gave me the 145amp alternator instead of the 105 and my belt was too short. Instead of getting a longer belt I went with the 105 amp alternator. What I found was causing the squeal was the new, GM, a/c tensioner. I bought a replacement from O'Reilly's because the dealer didn't have one and no squeal!. In comparing the two tensioners, they were identical parts, both made in Canada and you could see on the O'Reilly's one where the gm part # had been machined off. It was half the price too. I also got an idler pulley from O'Reilly's too. They were Gates brand.