What Causes the Abnormal Noise When the Car Air Conditioner is Turned to Maximum?

[Kieran]

There may be several reasons why a car makes a buzzing sound when the air conditioner is turned on: 1. A dirty air filter causing excessive noise and abnormal sounds; there may be too much dirt inside the air conditioner, and it is recommended to clean the air conditioner. 2. Debris in the blower fan blades causing abnormal noise. 3. Deformed blades in the air conditioner's exhaust fan, suggesting the need to replace the exhaust fan. Relevant information about car air conditioners is as follows: 1. Introduction: The car air conditioning device (air-conditioning-device), referred to as car air conditioning. 2. Function: It is used to adjust and control the temperature, humidity, air cleanliness, and air flow inside the car compartment to the optimal state, providing a comfortable riding environment for passengers and reducing travel fatigue; it creates good working conditions for the driver and plays an important role in ensuring safe driving as a ventilation device.

[SanHannah]

My car had the same issue before, the AC would buzz loudly when turned to max. Turned out the cabin air filter was clogged with leaves and dust, the blower had to work extra hard to push air through, no wonder it was noisy. Another time, a piece of plastic bag got tangled in the blower fan blades behind the glove box, making a sound like fighting fan blades. If you hear a clunking noise, it's probably loose bearings – get it fixed ASAP before a small problem becomes big. By the way, squeaking when turning on the AC could mean the compressor belt is worn and slipping, which is serious as it affects the entire cooling system. Changing the filter quarterly is crucial – I always check mine personally, it's super easy.

[GenevieveLee]

A friend who's been in the auto repair shop for ten years said that in summer, eight out of ten cars have this issue. There are several types of loud wind noises: a whooshing sound is mostly caused by paper or leaves stuck in the air duct, while a crackling sound usually indicates a broken plastic part on the air recirculation flap. If it's a metal grinding noise, that's more serious—it's likely the blower motor bearing is dry and worn out. The scariest is the compressor noise, like metal scraping against a metal bucket, which usually means the electromagnetic clutch is gone. He specifically emphasized never to spray perfume into the air vents—the sugar can stick to the fan blades and make things worse. Last time I visited his shop, I saw an Audi with a lollipop stuck in the blower motor, and it cost over 300 bucks to disassemble and clean it.

[VonEmiliano]

From an engineering structural perspective, the maximum airflow abnormal noise involves multi-system coupled vibrations. A mere 0.1mm offset in the blower motor shaft can trigger resonant whistling, and when wind speed reaches 7m/s, the centrifugal fan loses dynamic balance (similar to placing a vibrating phone on a table). Loose compressor high-pressure pipe clips can transmit low-frequency abnormal noises between 20-200Hz, while expansion valve icing blockage produces clicking sounds resembling bubble bursts. The liquid hammer sound caused by excessive refrigerant is more dangerous, akin to throwing glass beads into an iron barrel. It's recommended to first use a stethoscope to locate the noise source. Last time, I used Bluetooth earphones pressed against various components and found the loose evaporator bracket within half an hour.