Why does the car not cool when idling but works fine while driving?

[LeCaleb]

Here are the reasons why the air conditioning may not be cooling: 1. The AC expansion valve is blocked, preventing refrigerant circulation and thus failing to cool; 2. Abnormal operation of the AC hot/cold air door, causing the heating air door to open while driving; 3. Frozen evaporator core during driving, preventing cold air from blowing out (usually accompanied by reduced airflow); 4. System malfunction causing intermittent failure of electromagnetic clutch coil engagement; 5. Faulty electromagnetic clutch coil resulting in poor engagement.

[LaSkylar]

I've been driving for over a decade and often encounter AC cooling issues at idle. This happens because the engine runs at low RPM during idle, providing insufficient power to drive the AC compressor, naturally reducing cooling efficiency. When driving, the higher engine RPM allows the compressor to operate at full speed, restoring normal cooling. Another common cause is the cooling fan not spinning – at idle, the fan relies on electric power, and if the motor fails or the relay malfunctions, the fan won't work, preventing the condenser from dissipating heat. While driving, the incoming airflow helps significantly. I also recommend checking if the AC belt is loose – a loose belt can slip, affecting compressor performance. Additionally, when refrigerant is low, the system lacks sufficient pressure to function properly, with idle conditions being most affected. Overall, don't underestimate these issues; early inspection can prevent bigger problems.