Should the AC be turned on when using the car heater in winter?
2 Answers
In winter, there is no need to turn on the AC when using the car heater. This is because the working principle of the car heating system is different from that of the cooling system. The car heater utilizes the heat emitted from the exhaust pipe and radiator to warm the air, which is then blown into the cabin by the fan, without the need to activate the compressor. Using the heater does not significantly affect the car's fuel consumption. However, improper usage, such as turning it on too early, can cause the engine temperature to drop. If the system detects a drop in engine temperature, it will increase fuel injection to raise the engine temperature, which can then lead to an increase in fuel consumption.
As an ordinary driver, I rely solely on the heater to keep warm in winter without ever needing to turn on the AC. The heat comes directly from the engine, warming up the cabin without any extra fuel consumption. If I were to turn on the AC, it would engage the compressor and put additional load on the engine, noticeably increasing fuel usage while also making the car respond more sluggishly. My routine is to turn off the AC button as soon as I start the car, only adjusting the temperature knob higher. However, in cold weather, windows tend to fog up dangerously, especially after rain or snow—when the entire windshield gets misty, I briefly turn on the AC for about ten seconds to dehumidify and clear the fog, then immediately switch it off. This habit has saved me a significant amount on fuel costs, roughly tens of dollars each month. After making it a routine, I frequently check window conditions to prioritize safety, ensuring I never leave the AC running unnecessarily. In short, using the AC with the heater in winter is entirely redundant unless there’s an urgent need for defogging.
