Is it harmful to leave the car running with the AC on overnight?
2 Answers
Leaving the engine running with the AC on while parked can negatively affect your vehicle. Here are the relevant details: 1. Reasons: When the engine idles, its RPM is relatively low. Running the AC under these conditions leads to incomplete fuel combustion, which can cause carbon buildup in the engine cylinders and throttle body. Additionally, idling with the AC on increases fuel consumption. 2. Hazards: During engine idling, incomplete combustion produces exhaust containing high levels of carbon monoxide. This toxic gas may accumulate around the vehicle and enter the cabin through the AC system. With windows closed for AC operation, poor ventilation allows carbon monoxide concentration to gradually rise inside the vehicle, posing serious health risks to occupants over time.
From a safety perspective, I am deeply concerned about this issue. Leaving the car running with the air conditioning on all night in an enclosed space like a garage can cause rapid accumulation of carbon monoxide from the engine exhaust. This colorless, odorless toxic gas poses an extremely high risk of poisoning—inhaling even small amounts can lead to unconsciousness or even be fatal. Even outdoors, exhaust fumes can accumulate near the vehicle, endangering people or pets. Prolonged engine idling also increases the risk of overheating, accelerating component wear or causing cooling system failures. The continuous operation of the air conditioning compressor can lead to significant wear and potential refrigerant leaks. The battery may also be overloaded and drained, leaving the car unable to start the next day. Fuel consumption is another concern, with idling for an hour consuming approximately 0.5-1 liters of gasoline, wasting dozens of dollars in fuel costs overnight. For the safety of your family and community, I strongly recommend turning off the engine. If it is absolutely necessary, ensure proper ventilation and use a carbon monoxide detector.
