Why does the car air conditioning not cool at idle but cools when driving?
2 Answers
Common reasons why the air conditioning does not cool at idle but cools when driving: 1. Air conditioning compressor failure: The pressure between the air conditioning compressor and the expansion valve cannot reach 150Kpa to 200Kpa, preventing the refrigerant inside the system from circulating normally, causing the air conditioning not to cool at idle. 2. Expansion valve damage: The expansion valve cannot form high pressure, less than 150Kpa, so the evaporator behind it cannot cool down, leading to no cooling at idle. 3. Loose or broken air conditioning belt: If the drive belt is too loose, it will slip, accelerating wear and failing to transmit power, resulting in insufficient power at idle, thus not cooling enough. 4. Dirty condenser: The condenser is used for heat exchange. If the surface is too dirty or covered with too much dust, it will not cool, naturally causing the air conditioning not to cool. 5. Radiator blockage: The external cooling system will not dissipate heat well, leading to poor heat dissipation at idle, causing no cooling at idle. 6. Blower fan failure: There is abnormal noise inside, or the motor operates poorly, resulting in insufficient airflow.
Last time I was stuck at the highway exit, the A/C took forever to cool down at idle, but it became comfortable immediately after driving. A car-savvy buddy told me that at low idle speed, the A/C compressor doesn't work efficiently, reducing cooling performance. The fan speed also can't keep up, leading to poor heat dissipation—making the car feel like a sauna in summer. At the shop, they found the radiator clogged with dirt, and the problem disappeared after cleaning. Regular maintenance is key—clean the condenser periodically to avoid such issues. For safety, don't wait until a hot day to fix it; address it early for peace of mind.
