What Causes the Air Conditioner to Make Loud Noises When Turned On in a Car?

[MacRobert]

There are several reasons why the engine noise becomes louder when the car's air conditioner is turned on: Air conditioning pump noise: If there is an issue with either the electromagnetic clutch or the bearings inside the air conditioning pump, it can cause the pump to produce abnormal noises. Throttle valve clogging or sticking: If the throttle valve has carbon buildup or is sticking, it can lead to engine shaking and abnormal noises. Reasons for no air flow from the car's air conditioner: Blower fan malfunction: The car's blower fan is a crucial component for air flow from the air conditioner. If the air conditioning compressor fails during operation, the air conditioner will not produce air. Clogged air filter: The air filter is a significant and common reason for no air flow from the air conditioner. During operation, the car's air conditioner can accumulate many impurities from the air. Control system failure: This could be due to issues with the air vent, air conditioning computer, or control switch. Control system switches generally do not fail, and it is recommended that the owner visit a 4S shop for inspection to simplify the troubleshooting process.

[Ivan]

Back when I drove an older car, I also encountered the issue of loud AC noise. I later realized the sound mainly came from the blower area. If the blower bearings lack lubrication or accumulate dust, they can produce a tractor-like humming noise when spinning. Also, check if the air volume knob is set to the maximum setting—the highest fan speed naturally generates louder noise. Last time I removed the cabin air filter and found it clogged with willow catkins, completely blocking the air ducts, forcing the blower to work extra hard to push air through. These issues can be checked yourself: after turning off the engine, open the hood and listen for abnormal noises near the blower location; clearing leaves and debris around the AC air intake also helps. If the fan blades are warped or the bearings are completely worn out, you’ll need a professional mechanic to replace the parts.

[LaNorah]

Over the years in auto repair, I've encountered many cases of air conditioning noise, mostly concentrated in three areas. The blower motor is the prime suspect—when the bearing wears out and the gap increases, it starts clanking. Next, check the compressor belt tension; if it's too loose, it will slip and produce a sharp screech, especially noticeable during cold starts. Another often overlooked issue is foreign objects in the air ducts—once, I retrieved a child's toy stuck in a vent from a customer's car. My advice: first measure the voltage; if it's below 12V, there's an electrical issue. Then, lightly touch the blower to feel the vibration intensity. Finally, test the air conditioning line pressure—if the high pressure exceeds 300kPa, release the refrigerant immediately.

[AlexisAnn]

The issue of air conditioning noise requires case-by-case analysis. If it's a whooshing wind noise, it's likely due to debris stuck on the blower fan blades or a long-overdue cabin air filter replacement. For metallic scraping sounds, suspect insufficient lubrication in the blower motor bearings. Sudden high-pitched noises are most critical—they might indicate impending compressor seizure. Last month, my car had similar symptoms; it turned out the refrigerant was overcharged during the last service, causing compressor overload. When self-diagnosing, remember to turn off the audio system to pinpoint the noise source—the blower under the passenger footwell is particularly prone to issues. Also, loud initial operation during extreme heat is normal, but persistent noise after 10 minutes warrants attention.