Why does the car not cool at idle but works normally while driving?
2 Answers
Car not cooling at idle but working normally while driving can be attributed to the following reasons: 1. Proportional relationship: The engine speed and the car air conditioning compressor speed are proportionally related. When idling, due to the low speed, the car air conditioning compressor speed is correspondingly low. At this time, the low pressure in the air conditioning system will be higher, the expansion valve opening will be smaller, and the flow into the evaporator will also be smaller, resulting in less heat exchange in the evaporator. The direct manifestation is that you will feel the air conditioning is not cooling or the cooling effect is poor. 2. Cooling effect: When accelerating, the speed increases, the low pressure decreases, the expansion valve opening increases, the flow increases, the heat exchange in the evaporator increases, and the cooling effect improves.
I've driven many cars and encountered situations where the air conditioning doesn't cool properly at idle but works fine while driving. This is usually because at idle, the engine speed is low, resulting in insufficient power and reduced efficiency of the compressor. If the cooling fan isn't working at idle, the condenser can't dissipate heat effectively, leading to poor cooling performance. While driving, the airflow from the vehicle speed helps with heat dissipation, so cooling returns to normal. Another common reason is insufficient refrigerant or leaks, causing unstable pressure at idle. I once fixed this issue by cleaning the dirt off the condenser surface. Older cars are more prone to this problem, so it's advisable to check the fan operation, refrigerant level, and related fuses. Ignoring it might make you uncomfortably hot in traffic jams.
