What Causes Reduced Airflow from Car AC at High Speeds?
2 Answers
When a car's air conditioning suddenly stops cooling and the airflow decreases, the following reasons may exist: 1. Condenser: Excessive accumulation of impurities and dust on the condenser leads to poor cooling efficiency. 2. AC filter: Too many impurities in the AC filter affect the blower's air intake, reducing airflow. 3. Excessive impurities on the evaporator: Heavy contamination of the evaporator significantly impacts both the AC's air intake and cooling capacity, severely affecting its cooling performance. 4. Frost formation on evaporator surface: Ice buildup on the evaporator surface severely obstructs AC ventilation.
My friend who runs an auto repair shop mentioned that when a car's air conditioning airflow weakens at high speeds, the most common cause is a dirty cabin air filter clogging the air intake. Accumulated dust and debris can make the blower motor struggle to push out strong airflow. Another possible scenario is the blower motor's rotation speed failing to meet the demands of high-speed driving. At higher speeds, increased external air pressure can cause backflow into the intake, reducing output airflow. For automatic AC systems, faulty temperature sensors might misjudge conditions and automatically reduce fan speed. Frost buildup on the evaporator or minor refrigerant leaks could also diminish airflow. He recommends checking the filter before highway trips and replacing it every six months—it's an easy DIY job by removing the glove compartment. If the issue persists, inspect the blower motor's voltage supply or motor condition, as this is a common failure point in older vehicles that requires diligent maintenance.
