Air Flow and the Condenser
The air conditioner's refrigerant receives heat from the cabin through the evaporator core. The compressor pumps the refrigerant to the condenser as a vapor, where it condenses as it passes heat to the outside air. Condensation causes the refrigerant to change its state from a gas to a liquid. Without proper airflow, the refrigerant is unable to release this heat and transfers it back through the system.
Fans provide airflow while the vehicle is at rest. Airflow through the condenser is vital for automotive air conditioning performance. If its fan is not operating or spinning too slowly, its poor performance is more pronounced while the vehicle is at rest. While a vehicle is traveling forward, ram air is forced through the condenser.