What Causes Abnormal Noise When Turning On the AC in a Car?

[TannerFitz]

The reasons for abnormal noise when turning on the AC in a car include belt slippage, air conditioning compressor failure, or foreign objects in the air ducts. Below are detailed explanations: 1. Belt Slippage: The air conditioning compressor is driven by the engine crankshaft via a belt. If the belt becomes loose, aged, severely worn, or if the tensioner lacks sufficient tension, it can cause the belt to slip, resulting in abnormal noise. If the issue is due to the belt, simply replacing the belt will suffice. If the problem lies with the tensioner, then the tensioner needs to be replaced. 2. Air Conditioning Compressor Failure: When the AC switch is turned on, the air conditioning compressor starts operating. If the compressor is damaged, it may produce abnormal noise. In such cases, it is recommended to visit a 4S shop for part replacement and repair. 3. Foreign Objects in the Air Ducts: If there are foreign objects in the air conditioning system's ducts, these objects can rotate with the blower's airflow and repeatedly hit the air filter, causing abnormal noise. In this situation, the air filter can be removed, and the air ducts should be carefully inspected and cleaned of any foreign objects.

[VictoriaRose]

I've had several instances of strange noises from the air conditioning. I remember last summer when I turned on the AC while driving, there was a squeaking sound that really worried me. Later, when I took it to the repair shop, the technician said it was due to an aging belt. A loose or worn belt can easily cause friction noise when the compressor starts. It could also be due to foreign objects stuck in the fan blades or loose blades, or insufficient coolant, which might cause the AC system to make strange noises. It's recommended that car owners first check if the belt is tight and listen for the source of the noise. If the sound resembles metal clashing, it might stem from internal compressor issues, requiring professional diagnostic tools. If not repaired promptly, while the noise might not affect short-distance driving, it can worsen component wear and even lead to the entire AC system failing, costing both money and effort. It's best to check the belt's condition monthly as a preventive measure.

[LorenzoFitz]

As someone who frequently engages in car DIY, I find that abnormal noises from the air conditioning system are quite common, often caused by simple issues. For example, insufficient tension or cracks in the compressor belt can produce sharp noises, while dust blockage in the fan motor may result in a buzzing sound. The inspection process is straightforward: start the engine, turn off the AC to compare sounds, and confirm that the noise only occurs when the AC is on. Then, check the engine bay for any visibly loose components, especially around the belt and fan areas. Additionally, low refrigerant levels can cause the compressor to operate abnormally, producing a clicking sound. Replacing the belt or topping up the refrigerant yourself can save hundreds of dollars, but if the noise persists or worsens, it's best to consult a professional to check for compressor damage. Regular cleaning of the condenser and dust around the belt can significantly reduce such issues.

[DiEva]

From a safety perspective, air conditioning abnormal noises must never be ignored as they could signal serious issues. Worn compressor bearings will produce increasingly loud metal friction sounds during operation, and delayed repairs may lead to spontaneous combustion risks. A completely broken belt could affect other engine components. I recommend immediately stopping to check for foreign objects in the fan, using basic tools to test for current overload, and refilling refrigerant if necessary. While repair costs are modest, postponing maintenance may cause greater damage and compromise driving safety. Routine inspections of the AC system by technicians during regular maintenance can prevent potential hazards.