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What Causes the Engine to Make Noise When the Car's Air Conditioner is On?

2 Answers

MatthewMarie

07/24/25 10:09am

There are several reasons why the engine makes noise when the car's air conditioner is on: If the sound is not particularly loud, it is a normal phenomenon. This is because turning on the air conditioner increases the engine load, and the fan operates at high speed, resulting in louder noise. If the sound is particularly loud, there are several possible reasons: 1. Abnormal noise from the air conditioning pump. Any issue with the electromagnetic clutch or the bearings inside the air conditioning pump can cause abnormal noise. Noise from the electromagnetic clutch is mainly due to wear, which increases the gap, while noise from the air conditioning pump bearings is usually caused by a lack of lubrication. In severe cases, this can lead to the air conditioning pump burning out, rendering the cooling system inoperable. 2. Dirty or stuck throttle. Turning on the air conditioner increases the engine load, requiring the throttle to open wider to allow more air intake. If the throttle has carbon buildup or is stuck, it can cause engine vibration and abnormal noise. 3. Improper tension of the compressor drive belt. If the drive belt tension is incorrect, it can cause abnormal noise or even damage the air conditioning compressor. 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.

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OKayden

08/11/25 5:19am

I've been driving for twenty years, and every summer when I turn on the AC, I hear strange noises from the engine, mostly due to a loose belt. When the AC starts, the compressor load increases, and the squeaking sound is a sign of aging; a buzzing noise from a bad bearing is even more annoying. Frequent noises can indicate belt cracks or insufficient tension. A refrigerant leak in the compressor makes even more noise, and the fan spinning at high speed is normal. Don’t think it’s a small issue—fuel consumption will rise, and prolonged neglect could burn out parts. I always remind my friends to check and replace the belt regularly, about every six months; in the summer heat, noises are more common—don’t skimp by going to a roadside shop, find a proper repair shop, test the pressure first before fixing. A new belt costs just a few bucks, and taking care of small issues ensures safety.

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