Which Button is for the Rearview Mirror Heating Function?
4 Answers
The rearview mirror heating button icon is shaped like a square frame with three upward-curving arrows inside. The rearview mirror heating function refers to the ability of the rearview mirror to be heated by electric filaments embedded behind the mirror when driving in rainy, snowy, or foggy weather, ensuring a clear mirror surface. The rearview mirror heating function is particularly useful during rain or snow. When activated, the heater behind the mirror quickly warms the mirror surface, gradually removing rainwater or fog, eliminating the need for the driver to frequently wipe the mirror manually, thus reducing driving hazards. The usage of the rearview mirror heating function: There are generally two ways to activate the rearview mirror heating function. One is combined with the electric rearview mirror adjustment function button—simply rotating the knob can turn it on. The other is located on the air conditioning control panel—pressing the heating button will activate it. No manual angle adjustment is needed, as there is an adjustment button on the driver's side. The principle of the rearview mirror heating function: After pressing the button, the electric heater behind the rearview mirror glass rapidly heats up to a fixed temperature within a few minutes, typically between 35-60 degrees Celsius. The heat is then dissipated from the left and right rearview mirrors. Simultaneously, as the temperature rises and evaporation occurs, water droplets on the mirror surface become smaller, and fog gradually disappears, effectively heating the mirror and removing frost. However, if the rain is particularly heavy, the effect may diminish and become less noticeable. Precautions for using the rearview mirror heating function: The principle of rearview mirror heating involves adding electric heating filaments to the mirror. These filaments consume a significant amount of power. Therefore, when using the rearview mirror heating function, ensure the car is in an active state. Avoid activating the function when the car is stationary to prevent draining the car battery, which could leave insufficient power to start the car. Other methods for defogging rearview mirrors include: Opening windows for air convection: Crack open the side windows slightly to allow air exchange between the inside and outside of the car, reducing the temperature difference and gradually eliminating fog. Adjusting the car's air conditioning to the appropriate setting can use warm air from the AC to defog the mirrors.
I've been driving for several years, and the rearview mirror heating function is especially useful on rainy days. That button is usually combined with the rear window defroster, marked with a square containing curved wavy lines, and can be found near the air conditioning control panel. Pressing it activates the heating elements on both the rearview mirrors and rear window, clearing fog within minutes. However, this function shouldn't be used for extended periods as the system automatically turns off to prevent overheating damage. It's best avoided during summer heat as it may accelerate mirror aging. Some premium cars have a dedicated button labeled REAR, but most standard models combine it with the defroster function. Always check if it's turned off before parking to avoid draining the battery.
I've studied automotive electronic systems. The core of mirror heating is the resistance wire embedded behind the lens, which generates 40-60 degrees of heat when electrified. The control button is usually integrated with the rear window defogger switch, marked by a square icon with wavy lines. In circuit design, these two heaters are wired in parallel, so pressing one button activates both simultaneously. An automatic cutoff protects the heating wire from overheating, preset with a 15-minute auto-shutoff mechanism. This feature is particularly useful after winter snowfall, much safer than manually scraping off frost. If the mirror heating fails, the first step is to check whether the corresponding 15A fuse in the fuse box has blown.
My car is an economy model, and the rearview mirror heating button is located next to the air conditioning knob, marked with a rectangle and a wavy line. Every time it rains or fogs up in winter, pressing it clears the mirrors in about 5 minutes. Note that this function only works when the outdoor temperature is below 20 degrees Celsius, so pressing it in summer won't have any effect. When activated, an orange indicator light on the dashboard will illuminate to show it's working. I've noticed that this feature only works after the car is started, as using it when the car is just powered on might draw too much current and blow a fuse. Also, make sure the mirrors are completely dry after washing the car before turning on the heating to prevent short circuits.
