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In the past few weeks I have noticed a squeaking sound coming from the engine bay whenever I turn on my AC to cold or increase the power. When the AC temp is warm and power is low then there's no problem, but both lowering temperature and increasing power make the squeaking sound increase. I don't know much about AC compressors but I would have to guess it has something to do there. Should I just change my entire engine belt? Swap out the compressor? If the only possibility is to take it to a shop then I would rather not since I would rather just live with the noise rather than pay for labor. Any help would be appreciated.
 

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Drip water (a VERY small amount, literally just a little squirt at a time) onto the belt to see if it eventually shuts up. If it does, it's probably just a bad belt. Otherwise it may be the pulley, either way hopefully not a huge issue.
 

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if the noise goes away with the water test, the serpentine belt can be changed easily (on the 2.0 at least). If it fails the water test, then it's most likely the bearings wearing out.

The compressor is a possibility. If it's more than 100K miles and you use the A/C consistently, you'll need to replace the entire compressor. Shouldn't be too difficult except you need to vacuum the entire system (in a environmentally friendly way), and you're supposed to change the dryer once you expose the system to the open air. Otherwise, the moisture in the atmosphere will get in there, and since water doesn't compress, it'll break your new compressor soon after. And of course, you'll need to refill in the specific amount (by weight) of refrigerant afterwards.

You should also check other things along the belt path like the alternator, the tensioner, and the power steering if you don't have electric power steering. Take off the belt and spin them. If they aren't perfectly smooth or you hear some metalic rubbing sounds, then you've found the source of the noise.
 
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