Should the AC be turned on for defogging?
2 Answers
Under normal circumstances, the AC should be turned on for defogging. The AC is the control button for the air conditioning compressor. In essence, when the front windshield defogging function is activated in many car models, the AC is automatically turned on. The reason is that the AC has a dehumidification function, which can accelerate the efficiency of defogging. The causes of window fogging are as follows: 1. Temperature below the dew point: When the humidity in the air is constant, if the window temperature is below the dew point, condensation will form on the window surface, which is the common fogging phenomenon seen on the front windshield. 2. A certain temperature difference on both sides of the window: When the saturated vapor pressure on the surface with a lower temperature is less than the vapor pressure of the surrounding environment, water vapor gathers on the glass surface and seeps out in the form of tiny water droplets, forming fog.
Whether to turn on the AC for car defogging depends on the situation. I usually turn on the AC when the windshield fogs up while driving. This is because the air conditioning compressor can quickly reduce air humidity. Fogging is essentially condensation caused by the temperature difference between the inside and outside of the car, and turning on the AC is the most efficient way to remove moisture and defog. Turning on the AC in summer is natural, while in winter, you can turn up the temperature knob to combine warm air with AC, which defogs faster and saves fuel. On rainy or snowy days or when there are many people in the car breathing heavily, the AC is a must. However, during spring and autumn when the temperature is moderate, simply turning on the external circulation with high fan speed can also handle it. Remember that the windshield defogging button usually automatically activates the AC, while the rear window defogger uses heating wires and doesn’t require the AC.
