What causes the abnormal noise when the AC button is turned on?

[StEmilia]

The reasons for abnormal noise when the AC button is turned on are as follows: 1. Compressor: The metal friction sound produced when the compressor's electromagnetic clutch engages. The fault is usually due to a lack of lubricating refrigerant oil inside the compressor. When refrigerant oil is insufficient, the internal piston of the compressor does not receive adequate lubrication, resulting in metal friction sounds under the high pressure of the refrigerant. Another scenario is a fault with the electromagnetic clutch itself, where a damaged internal bearing causes abnormal noise. In this case, the compressor must be replaced. 2. Belt noise: The air conditioning belt may produce abnormal noise when subjected to excessive force. This situation occurs because the air conditioning system pressure rapidly increases when the AC is turned on.