What Causes One Side of Car Air Vents to Blow Cold Air While the Other Side Blows Hot Air?

[McCooper]

Car air vents blowing cold air on one side and hot air on the other can be caused by insufficient refrigerant, low efficiency of the air conditioning compressor, dirty condenser and evaporator, or malfunctioning air flaps. Here are the detailed explanations: Insufficient Refrigerant: When refrigerant is insufficient, the evaporation and heat absorption process of the liquid refrigerant entering the evaporator ends quickly, causing one side of the evaporator where the refrigerant flows in to absorb heat and cool down, while the side where the refrigerant flows out has no heat absorption effect. Low Efficiency of the Air Conditioning Compressor: If the air conditioning compressor is faulty and operates at low efficiency, the liquefaction of the refrigerant will be insufficient. In this state, the refrigerant entering the evaporator will have severely reduced heat absorption efficiency, leading to poor cooling performance, ultimately resulting in the airflow temperature from the vents failing to meet the standard. Dirty Condenser and Evaporator: If the car's air conditioning system is not cleaned for a long time, the condenser and evaporator can become covered with dust, lint, and other debris, weakening the refrigerant's effectiveness or reducing the heat absorption efficiency during the refrigerant's state change. This prevents the air from being fully cooled, leading to temperature differences in the airflow output from different vents. Malfunctioning Air Flaps: Faults in the air duct adjustment flaps or the flap drive motor in the air conditioning system can cause the air ducts to fail to close tightly.