Why Does My AC Rattle When I Turn It On?

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Your car’s AC system is designed to keep you cool and comfortable when temperatures rise. It’s designed to operate quietly and unobtrusively, so there should be little to no noise from an air conditioning system that’s in good working order. However, if you hear a rattle when you turn the air conditioning on, it could be any number of different problems.

While your air conditioner is technically a separate system, it’s tied to the rest of the engine by the serpentine belt. The serpentine belt is what’s responsible for turning the pulley at the AC compressor, and pressurizing the refrigerant lines. The compressor engages/disengages by an electromagnetic clutch.

If you turn on the AC and immediately hear a rattling noise, there are a few potential causes:

  • Compressor: If your AC compressor is beginning to fail, it can make a rattling noise.

  • Pulley: If the compressor pulley bearings are failing, they can make noises, generally a grinding, roaring or squealing noise.

  • Belt: If the serpentine belt is worn, it can slip when the compressor engages, causing noises.

  • Idler Pulley: It’s possible that the noise is actually from the idler pulley if its bearings are failing. The noise would start when the compressor engages due to the increased load on the engine.

  • Compressor Clutch: The compressor clutch is a high-wear item, and if it’s worn out, it can create a rattle during operation. Some vehicles can have only the clutch replaced, but some require replacement of both the clutch and compressor.

There are many other potential sources of the noise as well. When the AC turns on, it puts the entire engine under a heavier load. This increased load can cause rattles from things like the power steering pump pulley, loose parts (even a loose hood prop rod can rattle under th additional vibrations created by operating your air conditioner). If you hear a rattle in your car, have a mobile technician from YourMechanic inspect the cause of the sound.


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YourMechanic AC is not working Inspection Service

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Number of Reviews

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Rating Summary
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Oreste

12 years of experience
111 reviews
Oreste
12 years of experience
Nissan Sentra - AC is not working - Miami, Florida
Oreste is extremely knowledgeable and professional. He fixed my car quickly and knew exactly what I was asking about and made me felt confident I was getting excellent service. He is a pleasure to work with and I highly recommend him!
Mini Cooper - AC is not working - Miami, Florida
Excellent mechanic , he know all abou the Minicooper engines , he fixed the fail and check all , he did a great job

Joe

41 years of experience
704 reviews
Joe
41 years of experience
BMW 740i - AC is not working - Saint Petersburg, Florida
Great guy. Knows his stuff and easy to work with. Very friendly and helpful. Knows BMW and that’s important to me. Highly recommend.
Honda Odyssey - AC is not working - Tampa, Florida
As expected - Joe was great. Insightful, helpful and explained everything. Will book again without hesitation.

Brian

21 years of experience
238 reviews
Brian
21 years of experience
Honda Odyssey - AC is not working - Jacksonville, Florida
Very knowledgeable and courteous. He was able to quickly diagnose the problem and tell us how to fix it! Thanks Brian!!
Nissan Rogue - AC is not working - Jacksonville, Florida
Amazing service!!! Brian was timely, professional, informative, and this service is just SO convenient. This was my 2nd time booking with Brian via Yourmechanic.com and it wont be my last!!

Benji

20 years of experience
62 reviews
Benji
20 years of experience
Jeep Grand Cherokee - AC is not working - Paradise Valley, Arizona
Benji was beyond professional and handled our issue with speed. Super efficient and went above and beyond!
Land Rover Range Rover - AC is not working - Scottsdale, Arizona
Very knowledgeable! On time, kind, Courteous. Definitely a master technician. Identified the issue Immediately and resolved quickly! A pleasure to work with.

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