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Q: My car AC make noise when on but quiet when off. I just replaced the entire system less than 2 years ago?

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There is a rattling noise, but AC does still blow cold. From time to time it makes a loud humming noise. It is a Hyundai Sonata 2004, 4 door car.

It sounds like you may have an internal component of the AC compressor failing. It is possible to be a bearing or another non serviceable item. I suggest having a certified technician, like one from YourMechanic, diagnose the noise firsthand to determine the exact cause of your concern.

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