Why does the car air conditioner cool when parked but not when driving?
2 Answers
Car air conditioner not cooling when parked but cooling when driving is generally caused by insufficient pressure. Here is the relevant information: 1. Lack of Freon: When the car is idling, especially when stopped at a red light or in traffic, the lack of wind speed cooling from driving occurs because the engine speed is low, causing the compressor speed to also decrease relatively. If there is a lack of Freon, the instantaneous pressure increase cannot reach the standard state. This results in excessively low high pressure, leading to unsatisfactory cooling performance. 2. Compressor pressure leakage: This directly causes severely low pressure during idling. This situation requires replacing the compressor, which is a significant expense. 3. The air conditioning radiator fan is not working: When parked, poor heat dissipation causes excessively high pressure, and the high-pressure sensor forces the compressor to stop working, resulting in no cold air. In this case, check the fuse, relay, and the fan itself to identify the faulty component and replace it.
I've encountered this issue several times. When the air conditioning isn't cool while parked but works fine while driving, it's often because the fan isn't functioning properly during operation or the engine compartment heat is too high, affecting the cooling system. If the fan only runs when parked but not while driving, it could be due to a stuck fan motor or loose control wiring, especially when wind cooling at high speeds isn't sufficient to compensate. Another common cause is aging or slipping compressor belts, leading to poor compressor performance as engine RPM increases during driving. Additionally, insufficient refrigerant or minor leaks may appear stable when parked but become more severe when driving exposes leakage points due to airflow. I recommend first checking the fan's operation by listening for a humming sound with the engine off. If normal, start the engine and test again. If the issue persists, visit a professional shop to inspect the compressor or recharge the refrigerant.
