Why Does the Engine Sound Louder When the Car's Air Conditioner is On?

[Amy]

Here are the possible reasons why the engine sounds louder when the car's air conditioner is on: 1. Dirty or stuck throttle valve: Turning on the air conditioner increases the engine load, requiring the throttle valve to open wider to allow more air intake. If the throttle valve has carbon buildup or is stuck, it can cause engine vibration and unusual noises. 2. Improper tension of the compressor drive belt: If the drive belt tension is incorrect, it can cause unusual noises in mild cases or damage the air conditioning compressor in severe cases. The principle is that if the drive belt is too loose, the electromagnetic clutch will slip; if the drive belt is too tight, the load on the electromagnetic clutch will increase.

[Patricia]

I've encountered similar issues several times. When the air conditioning is turned on, the engine noise increases mainly because the AC compressor adds extra load to the engine, just like breathing heavier when running with a load. The compressor is responsible for cooling and requires engine power to operate, while the cooling fan also needs to run at high speed to cool the system. All these operations make the engine work harder, naturally amplifying the sound. If the noise is particularly noticeable, it might involve a loose or worn belt, such as a failing tensioner causing squeaking, or loose engine mounts amplifying vibration noise. I recommend starting with simple checks, like inspecting the belt's condition and identifying the noise source, followed by regular maintenance of the AC system. For safety, don't ignore persistent loud noises that can distract you while driving. It's best to have a professional mechanic check it to prevent minor issues from turning into major repairs.