Why Doesn't the Car Cool When Stopped at a Red Light?

[DeLawson]

When a car stops at a red light and doesn't cool, it's because the fuel-saving auto start-stop function is activated. Here are the details about why a car doesn't cool when stopped at a red light: 1. Definition: The auto start-stop function of a car refers to the engine automatically shutting off when the vehicle comes to a temporary stop during driving. Under certain conditions, the engine can shut off automatically, and when the vehicle needs to continue moving, the driver can resume driving by pressing the accelerator. 2. Function: The core of the auto start-stop system is to automatically control the engine's shutdown and restart. The auto start-stop system allows the vehicle to temporarily turn off the engine during brief stops, avoiding unnecessary fuel consumption.

[KinsleyMarie]

When the car is idling at a red light and the air conditioning is not cooling properly, I believe the main reason is that the engine speed is too low, causing the efficiency of the air conditioning compressor to drop. The air conditioning system relies on the engine to drive the compressor for cooling, but at idle, the engine speed is only a few hundred revolutions per minute, resulting in insufficient power and reduced cooling capacity. Additionally, the cooling fan may not be operating at full speed, allowing heat to accumulate in the engine compartment, which affects the air conditioning's heat dissipation efficiency. I've observed many vehicles, especially older models, where faulty fans or insufficient refrigerant exacerbate this issue. It's advisable to check the refrigerant level and fan functionality before using the car in summer, or to keep the air conditioning running while the vehicle is moving to avoid discomfort. Furthermore, when idling at a red light, try to turn off unnecessary electrical devices to reduce the engine load, which might slightly improve the air conditioning performance. However, the best solution is to have a professional inspection to prevent long-term issues.

[AdalineDella]

It's really annoying when the AC doesn't cool properly at red lights. From my driving experience, this is mostly related to the idle state. When the car engine runs at low speed, the compressor doesn't rotate fast enough, resulting in poor cooling performance—just like a slow-spinning fan can't produce strong wind. This is especially noticeable in hot weather. I suspect dust buildup on the radiator or condenser is blocking airflow, preventing the temperature from dropping. Additionally, if there's a slight leak in the AC system, insufficient refrigerant can worsen the problem. I recommend regularly cleaning the radiator surface during maintenance and checking refrigerant pressure to avoid turning the car into an oven at red lights. Having driven different cars, I've noticed newer models might fare better, but older vehicles are more prone to this issue. Keeping the windows slightly open can provide temporary relief, but it's best to schedule regular inspections to prevent future troubles.

[Logan]

I encountered a situation where the car's air conditioning stopped cooling when idling at a red light. My first thought was a maintenance issue with the AC system. The most common causes are compressor clutch or fan failure, leading to insufficient cooling during idle due to inadequate heat dissipation. Refrigerant leaks or pipe blockages can also cause system failure. It's recommended to simply check if the fan is spinning or measure the refrigerant pressure - most of the time minor repairs can solve the problem. Regular maintenance of AC components, such as cleaning the condenser, can prevent heat wave discomfort during traffic jams.