What Causes the Loud Buzzing Noise When Turning the Car AC to High Speed?

[McFrancisco]

Reasons why the buzzing noise increases with higher fan speed when the AC is on: 1. The blades of the exhaust fan inside the AC are deformed, and it is recommended to replace the exhaust fan. 2. The motor of the exhaust fan inside the AC is damaged, and it is recommended to replace the exhaust fan. 3. There is excessive dirt inside the AC, and it is recommended to clean the AC. Additional Information: Car Air Conditioning System: Commonly referred to as car AC. It generally includes a refrigeration device, a heating device, and a ventilation device. This combined system makes full use of the limited space inside the car, with a simple structure and easy operation, making it a popular modern car air conditioning system internationally. Functions: 1. Used to adjust and control the temperature, humidity, air cleanliness, and airflow inside the car cabin to the optimal state; 2. Provides a comfortable riding environment for passengers.

[DelJayce]

I have experience dealing with many similar issues. When the car AC makes loud buzzing noises at high fan speeds, it's mainly due to problems with the blower fan. The fan blades may be deformed or the bearings worn out, causing buzzing sounds during high-speed rotation. Another common reason is foreign objects blocking the AC ducts, such as fallen leaves getting stuck, which disrupts airflow and creates noise. Additionally, a heavily clogged AC filter that hasn't been replaced can accumulate dust, making air circulation difficult and generating buzzing noises. In my last repair case, a customer had extremely loud noises at high fan speeds, and upon inspection, we found the fan motor had aged. Replacing it solved the problem. Don't ignore this issue – prolonged neglect could damage the motor or ducts. It's best to have a repair shop thoroughly check the filter, fan, and ducts to avoid higher costs later. Regular cleaning of air intakes can also prevent such problems, especially during seasons with many leaves like spring and autumn.

[StMaggie]

My car also experienced this issue before, where the AC made a loud thunder-like noise when set to high fan speed. The reasons are usually simple, such as debris blocking the air intake, causing the fan to make noise when it spins; or a dirty air filter that hasn’t been replaced, leading to poor airflow and increased noise. It could also be due to loose or deformed internal fan blades. Last time I checked myself, I found a piece of paper had fallen into the air duct under the glove box—removing it fixed the problem. If the fan motor is worn out, it can also produce noise and will need replacement. Don’t force the AC to run when it’s noisy, as it consumes more power and can damage the motor. I recommend first checking under the hood for any blockages in the air intake and cleaning it out. If that doesn’t help, consult a technician. Developing a habit of checking the air filter monthly saves a lot of hassle—otherwise, the problem could worsen, leading to louder noises or reduced cooling performance.

[WalkerAnn]

When the air conditioner makes a loud buzzing noise at high fan speed, it's mostly due to fan issues. Damaged fan blades or faulty bearings cause noise during rotation; or loose/disconnected air ducts create strong vibration sounds during operation; clogged filters restricting airflow also lead to buzzing. If the motor is aging or the capacitor fails, the noise becomes even louder. Upon noticing such noises, inspect these points promptly - otherwise, it may reduce AC efficiency and potentially affect driving safety. For those with DIY skills, removing and cleaning or replacing the filter is a low-cost solution; otherwise, seek professional repair to avoid more expensive fixes later.