Why does the car air conditioner sometimes blow air and sometimes not?

[McEmmanuel]

Sometimes it blows air and sometimes not. When the air conditioner is first turned on, everything works normally, but after a while, you can only hear the blower running, but no air comes out. The reason for this phenomenon is that the evaporator coil is frozen. The air blown by the blower must first pass through the evaporator coil to be cooled before cold air is produced. However, if a layer of ice forms on the surface of the evaporator coil, the air cannot pass through, making it seem like no air is blowing out even though the blower is still running. Causes of evaporator coil freezing: 1. Damaged temperature sensor on the evaporator coil: It fails to detect that the evaporator is about to freeze, so the compressor does not shut off and keeps running, leading to freezing. 2. Faulty variable displacement valve: Some compressors have a variable displacement valve, and if this valve is damaged, the compressor will not shut off, resulting in freezing. If this issue occurs after a recent refrigerant recharge, it could also be due to an incorrect amount of refrigerant. Before recharging, the system must be vacuumed, and then the refrigerant should be filled according to the standard quantity specified for the vehicle.