What Causes the Squeaking Noise from a Car's Air Conditioning Belt?
3 Answers
Reasons for abnormal noise from a car's air conditioning belt: Loose compressor belt: Insufficient belt tension, which can be adjusted. Excessive refrigerant high pressure:
I noticed that whenever I turn on the car's AC, the belt makes this annoying high-pitched squealing noise—almost like nails on a chalkboard. Nine times out of ten, it’s because the belt is either loose or worn out. Last time this happened, I checked it myself: if the belt surface feels glossy, has frayed edges, or even cracks, it definitely needs replacing. Also, if the belt grooves are clogged with dust or engine oil, it’ll slip and screech. Oh, and once I parked under a tree, and later found fruit residue and tree sap stuck in the engine bay—the moment the belt flicked that gunk, it started whining. When I took it to the shop, the mechanic used a special tool to measure the tension and said it was way off. After tightening it, the noise vanished instantly. Now, especially during rainy seasons, I always keep an eye on the belt’s condition.
Car air conditioning belt noise usually falls into three scenarios. The most common is belt slippage due to being too loose - you'll notice obvious belt bouncing during operation, which can be fixed by adjusting the tensioner. The second is aging/cracking of the belt itself, especially on vehicles with 70,000-80,000 km where the inner side gets worn smooth and the rubber hardens like plastic sheets - this requires complete belt replacement. The third is contamination; I once found noise after maintenance caused by oil accidentally dripping into belt grooves during an oil change by a trainee. Some ask if dashboard wax can silence the noise? Absolutely not - oil-based liquids corrode rubber, causing worse wear after temporary quietness.
