Why does the car air conditioner sometimes blow cold and sometimes hot?

[VonPeter]

The reasons why a car air conditioner sometimes blows cold and sometimes hot include: loose wiring of the compressor; poor contact of the pressure switch; poor contact of the relay; or a faulty compressor clutch. Additional information: 1. High-temperature gas cools into liquid: When the air conditioner is first turned on, the compressor starts working, compressing the gaseous refrigerant in the system into a high-temperature, high-pressure gas, which is then sent to the condenser for cooling. After cooling, it becomes a high-temperature, high-pressure liquid, which is dried and filtered through the dryer bottle, then passes through the expansion valve and evaporator before returning to the compressor. 2. High-temperature, high-pressure liquid expands: When the high-temperature, high-pressure liquid passes through the expansion valve, it undergoes a drastic change, turning into a low-temperature, low-pressure liquid. These low-temperature, low-pressure liquids cause the temperature of the evaporator to drop rapidly, so the air blown by the air conditioner motor becomes cold after passing through the evaporator.