How long can a car idle with the engine running and AC on?
4 Answers
The following are reasons why a car may stall when idling: 1. Misoperation: Especially for beginners, such as wrong gear selection, excessive braking, clutch-throttle coordination issues, or accidentally turning off the ignition with the key. Restarting the engine usually solves the problem. 2. Dirty throttle body/idle control valve: Mostly occurs during idling, often accompanied by engine shaking. Lightly pressing the accelerator when restarting can help the engine start. It's recommended to clean the throttle body promptly. 3. Fuel system failure: Causes include poor fuel quality, fuel exhaustion, fuel pump burnout, clogged fuel lines, faulty fuel pump fuse, or defective fuel pressure sensor. Inspect relevant components. 4. Ignition system failure: Includes spark plug issues, faulty ignition coils/modules, or aged spark plug wires. Check related components. 5. Throttle body/idle control valve malfunction: These are crucial components in the engine intake system and relatively precise parts. Many cases of stalling or failure to start are caused by damaged throttle assemblies or idle control valves.
I've been driving for over a decade and this is a common issue. When you're parked waiting for someone or resting with the engine running and the AC on without moving, how long can it last? It depends on the car's condition. With a healthy battery and normal engine in cool weather, it can last 40 minutes to an hour without issues. But in hot summer temperatures or with an aging battery, it might only last about 20 minutes before the battery runs low, and the engine could overheat, triggering a warning light. Once, I forgot to turn off the AC while waiting for family at a mall, and after 20 minutes, the car struggled to start, almost failing, and I had to call for roadside assistance. The lesson is clear: unless it's an emergency, avoid prolonged idling. You can turn off the AC in advance and switch to opening the windows for ventilation. The AC compressor drains the battery, and at idle, the alternator can't keep up with recharging, leading to wasted fuel and potential damage over time.
From the perspective of vehicle operation principles, when the engine is running and the air conditioning is turned on, the compressor relies on the engine to drive it. In this scenario, if the car is stationary, how long can the air conditioning operate? The battery and cooling system are crucial. If the battery is in good condition, the alternator can still provide some charge to the battery during idle, allowing it to last 30 to 60 minutes. However, if the battery is old or the weather is hot, and engine cooling is poor, it may only last 10 to 15 minutes before risking overheating or battery drain. As a car enthusiast who regularly maintains my vehicle, I avoid this habit as it increases carbon buildup and wastes approximately 0.8 liters of fuel per hour. It's advisable to let the car run for a while before turning on the air conditioning or to turn off the engine if parked for more than 10 minutes, using the fan for temporary cooling. This practice helps extend component lifespan and prevents minor issues from escalating into major faults.
Saving money and fuel is my top concern, so I've researched this issue. Running the engine with the AC on while stationary is actually very resource-intensive. When the engine idles, it consumes more fuel than when driving, burning up to 1 liter per hour, and the AC increases the load. Generally, it's acceptable for up to half an hour; otherwise, the fuel gauge drops quickly, and the battery may drain from 100% to insufficient levels. Long-term idling also pollutes the air and increases carbon emissions. I often tell my friends to try turning off the AC when parked or just using the external air circulation for ventilation. Each time you do this, you can save a few dollars and feel better about being eco-friendly. Keep the duration short, like 15 minutes—don't sacrifice your car and wallet for temporary comfort.
