When a car's air conditioning system blows cool air while the car is in motion but becomes warm when the vehicle is parked or in slow-moving traffic, it is likely due to one of the following issues:
Low Refrigerant Level: The most common reason for such behavior is a low refrigerant level in the air conditioning system. When the car is moving, the compressor runs faster, and the higher pressure helps to circulate the refrigerant and produce cooler air. However, when the car is stationary or moving slowly, the compressor may not be running at optimal speed, leading to warmer air being blown into the cabin.
Malfunctioning Cooling Fan: The cooling fan is responsible for dissipating heat from the air conditioning condenser, which releases heat absorbed from the cabin. If the cooling fan fails to operate correctly or runs at a reduced speed, the condenser may not cool down efficiently, resulting in warmer air when the car is not in motion.
Clogged Condenser or Evaporator: Accumulation of dirt, debris, or other contaminants on the condenser or evaporator can impede the heat exchange process, causing the air conditioning system to function less efficiently, particularly when the car is stationary or moving slowly.
Faulty Compressor Clutch: The compressor clutch is responsible for engaging and disengaging the compressor with the engine. If the clutch is failing or slipping, it may not work correctly when the car is idling or moving at low speeds, leading to insufficient cooling.
Expansion Valve or Orifice Tube Issues: The expansion valve or orifice tube regulates the flow of refrigerant through the system. If these components are clogged or malfunctioning, they can disrupt the refrigerant flow and cause temperature inconsistencies.
Electrical Issues: Problems with electrical connections, sensors, or the air conditioning control module can also lead to erratic cooling behavior.
To pinpoint the exact cause of the issue, it is recommended to take the car to a qualified mechanic or an automotive service center. They can perform a comprehensive diagnosis of the air conditioning system using specialized tools and equipment, identify the problem, and perform the necessary repairs or maintenance to restore proper cooling performance.