Skip the auto shop - Our mechanics make house calls

Why Does My AC Rattle When I Turn It On?

AC Rattling

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP)...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...


Related questions

Q: How do I use the Pass Temp feature?

The Pass Temp feature allows you to change the temperature between the driver and passenger side. This makes them the ride more enjoyable for both the driver and passenger. To use the Pass Temp feature: Press the Pass Temp...

Q: How do I quickly heat the cabin of the vehicle?

If it is cold inside your car’s cabin, you can use the climate controls to quickly heat up the car. To heat the cabin quickly, follow these quick steps: 1. Use the fan control dial to set the fan speed...

Q: My car makes a grating noise while applying the brakes to turn

It sounds like you need to check your front brakes. Most of the braking is done with the front brakes, therefore they tend to wear out more quickly than the rear brakes. If you let it go too long, you...