Which Button is the Rearview Mirror Heater?
4 Answers
The rearview mirror heater button is typically marked with a rectangle containing three upward-curving arrows. The car's heating button activates electric heating wires embedded behind the mirror to reduce moisture, fog, and frost on the front and rear windshields and exterior rearview mirrors, thereby improving the driver's visibility and ensuring clear mirror surfaces. This enhances driving safety. Methods to activate the rearview mirror heating function: There are generally two ways to activate the rearview mirror heating function. One is combined with the electric mirror adjustment button—simply rotate the knob to turn it on. The other is located on the air conditioning control panel—press the heating button to activate it. No manual angle adjustment is needed, as the driver's side has adjustment buttons. 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 (usually between 35-60 degrees Celsius) within minutes. The heat is then emitted from the left and right rearview mirrors. As the temperature rises and evaporation occurs, water droplets on the mirror surface gradually shrink, and fog slowly dissipates, effectively clearing frost and fog from the mirror. However, in heavy rain, its effectiveness may diminish and become less noticeable. Precautions for using the rearview mirror heating function: The principle of rearview mirror heating involves electric heating wires on the mirror, which consume significant power. Ensure the car is running when using this feature to avoid draining the battery, which could prevent the car from starting. Other methods for defogging rearview mirrors include: Opening windows slightly to create airflow between the inside and outside of the car, reducing temperature differences and gradually eliminating fog. Adjusting the car's air conditioning to the appropriate setting to blow warm air for defogging.
The location of the rearview mirror heating button varies significantly by model. The most common is the mirror icon button with wavy lines, usually found near the window control area on the driver's door panel. In my old Toyota Corolla, it was activated by pressing the center of the mirror adjustment knob, while my new Tesla Model 3 turns it on via the touchscreen in the climate control interface. This feature is especially useful in rainy weather, instantly clearing fog during highway driving. A reminder: it takes about 3 minutes to take effect after activation—repeatedly pressing it too soon may damage the circuit. Some base models may lack this feature; if retrofitting, pay attention to waterproofing the wiring.
Last time a friend asked where this button was, I noticed how designs vary wildly across brands. German cars like Volkswagen prefer placing it in the center console's AC zone, lined up with seat heating buttons; Nissan's Sylphy integrates it directly with the rear window defroster button - pressing it simultaneously heats both mirrors and rear glass. The icon typically shows two stacked rectangles with an upward arrow or a heating coil symbol. Note it only activates automatically below 5°C in winter - pressing it in summer does nothing. If your mirrors keep fogging but you can't find the button, your model likely doesn't have this feature.
When I first started driving, I also spent a long time looking for the mirror heating button. Later, I discovered that the Hyundai ix35 has a clever design—just turn the mirror adjustment knob to the heating icon position. Nowadays, mainstream designs fall into three categories: physical buttons on the door or center console, options in the touchscreen menu, and the two-in-one type integrated with the rear window defroster button. After activation, the heating element takes about 90 seconds to warm up, which can help avoid repeatedly turning the wipers on and off during rainy days. However, aging wiring in older cars can easily lead to heating failure, in which case you need to check the 15A blue fuse in the fuse box.
