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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Recent AC is not working Inspection reviews

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YourMechanic AC is not working Inspection Service

Average Rating

4.9/5

Number of Reviews

921

Rating Summary
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John

26 years of experience
597 reviews
John
26 years of experience
Isuzu Trooper - AC is not working - League City, Texas
John is the man. Super friendly, keeps you in the loop on everything he’s doing and fixed all my issues quick and under my budget. I will recommend John to everyone I know. Thanks again John.
Infiniti QX70 - AC is not working - Manvel, Texas
John is a lovely human being. He was able to fix my Xfinity QX70 Air-conditioning in such a timely fashion. He was profession, kind, and focused. It was convenient coming to my home garage. He wore mask and gloves and wiped down my car after as I am autoimmune compromised during Covid. And the price was so cheap. I will definitely use him again!!!! Thank you so much!

Jay

36 years of experience
764 reviews
Jay
36 years of experience
Isuzu Trooper - AC is not working - Upland, California
Jay can best be described in one word - AWESOME! It's no wonder that customers fight over his appointment slots ...
Chrysler 300 - AC is not working - Rancho Cucamonga, California
JA Y IS THE BEST. HE HAS BEEN SERVICING MY WIFE'S 1999 TRANS AM FOR YEARS. NOW I NEEDED SERVICE ON MY 201 6 CHRYSLER 300S. I HAD A STRANGE AC PROBLEM AND JAY FIGURED IT OUT..

Joe

42 years of experience
745 reviews
Joe
42 years of experience
Honda Civic - AC is not working - Oldsmar, Florida
Joe was personable and efficient. He took the time to explain what was needed and fixed my ac problem.
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.

Honorio

18 years of experience
824 reviews
Honorio
18 years of experience
Nissan Altima - AC is not working - San Jose, California
Honorio was such an amazing mechanic. He is super smart and knowledgeable about what he’s doing. You don’t have to second guess him twice. Th way he puts so much effort into his work you would think he’s fixing his own car. He really cares and wants to do the best possible job. He is an amazing mechanic and will definitely be booking him from now on.
Ford Mustang - AC is not working - Los Altos, California
Honorio, was a Star, will be looking to book him for follow up work after my AC diagnoses, refill and ID of the main problem. More than 5 stars if that were possible

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