Does idling with the air conditioning on damage the car?

[XavierMarie]

Idling with the air conditioning on can damage the car. There are three main reasons why idling with the air conditioning on is harmful: 1. Idling with the air conditioning on can cause incomplete combustion in the engine, increasing carbon deposits inside the engine. If the air conditioning is left on while idling for extended periods, carbon monoxide poisoning may occur inside the car, which is harmful to both the vehicle and the occupants; 2. When the car is idling (stationary without pressing the accelerator), the fuel reacts with oxygen in the air but does not burn completely, producing more exhaust gases containing carbon monoxide; 3. Carbon monoxide can accumulate around the car, and the longer the duration, the higher the concentration. If the car is set to external air circulation, a significant amount of carbon monoxide from outside can be drawn into the car, leading to carbon monoxide poisoning.

[DelSkylar]

I worked in a repair shop for over ten years and often encountered car owners asking this question. Idling with the air conditioning on does put extra strain on the engine, and it's not good in the long run. At low RPMs, the engine has to drive the compressor, and incomplete fuel combustion can easily lead to carbon buildup. The more carbon builds up, the more fuel the car consumes. Especially on hot days when idling with the AC on, the fan runs loudly and the water temperature tends to rise, accelerating the aging of engine compartment rubber pads over time. Nowadays, whenever I see car owners idling with the AC on in parking lots, I always remind them not to exceed half an hour—it’s better to step out and take a break. Regularly cleaning carbon deposits from the throttle body is also essential; otherwise, by the time the engine starts shaking, it might be too late to fix.

[EverettLee]

As a car owner who prioritizes vehicle maintenance, I believe this issue should be considered in terms of duration. It's fine to run the AC briefly while waiting, such as the ten minutes spent picking up or dropping off kids. However, taking a two-hour nap in the car with the AC on means the engine runs at low RPM for an extended period, leading to incomplete fuel combustion and inevitable carbon buildup, which can eventually affect the exhaust system. I once calculated that idling with the AC on consumes about two liters of fuel per hour—costly and harmful to the car. Nowadays, during summer, if I need to park for a long time, I either go to a café or park in the shade with the windows open for ventilation. Regular intake cleaning also helps significantly in reducing carbon buildup issues.

[SimonDella]

My friends and I often encounter this situation during road trips and have discussed it many times. Simply put, idling with the AC on will definitely increase fuel consumption, and the engine has to work harder. However, modern cars are well-built, so occasionally running the AC for 20 minutes is absolutely fine. Last year during a long drive, I slept in the service area with the AC on for 40 minutes, and later checks showed no issues at all. The key is to avoid doing this in an enclosed garage, as exhaust fumes can't escape and may lead to poisoning. If you idle with the AC on for several hours every day, carbon buildup in the engine will worsen, potentially requiring a major overhaul in two or three years, which can be quite costly.

[SanOscar]

This issue should be considered based on actual conditions. Parking in the open under high temperatures for just five minutes without air conditioning can cause heatstroke, so turning it on is a must even if it harms the car. However, prolonged idling with the air conditioning on poses two main problems: first, the low RPM increases the engine load due to the air conditioning compressor, leading to poor combustion efficiency and carbon buildup; second, stationary vehicles have poor heat dissipation, making them prone to overheating in high temperatures. My experience suggests turning off the engine if idling exceeds half an hour, and using a fan powered by a charging station when necessary. Additionally, older vehicles require extra attention as aged components are more prone to malfunctions, while newer cars are relatively more durable.