When idling with the air conditioning on, what you need to be concerned about is the engine's temperature, especially in older cars that use mechanical fans. Mechanical fans are driven by the engine's crankshaft, and at idle, the engine's crankshaft rotates more slowly, causing the cooling fan to spin at a lower speed. Prolonged idling can lead to insufficient engine cooling and result in overheating.
Effects of idling with the air conditioning on:
1：Fuel consumption: Cars consume fuel when idling, and running the air conditioning system requires the engine to power the compressor, which increases fuel consumption.
2：Shortened battery life: The air conditioning fan is powered by the car's battery, and during idle, the battery's charging efficiency is relatively low. Running the fan can potentially lead to the battery discharging, which, over time, can shorten the battery's lifespan.
Does idling with the air conditioning on lead to carbon buildup?
It's important to note that any time the engine is running, the car will produce carbon buildup. Idling with the air conditioning on during idle does not significantly contribute to carbon buildup. The extent of carbon buildup while idling with the air conditioning on is quite minimal. The carbon buildup during idle is comparable to that during steady-speed driving. In fact, carbon buildup is much less significant during idle compared to the acceleration and deceleration phases when the car is in motion.
Additionally, it is correct that less carbon buildup occurs when the car is parked and the engine is turned off since the engine is not running and, therefore, not producing carbon. However, if the car has been recently cold-started and the engine has not reached its optimal operating temperature, it's best to keep the engine idling. This is because, when the engine hasn't reached its optimal operating temperature, the fuel pump typically delays its operation for a while. If the car is turned off before the engine reaches the optimal temperature, any unburned gasoline in the engine won't be combusted, and after the gasoline evaporates, the remaining impurities can form carbon buildup.
