Where is the rearview mirror heating switch for the 3 Series?
2 Answers
The rearview mirror heating for the 3 Series is a button-type switch located among the buttons below the central control screen. Its icon features three curved upward arrows paired with a rectangle. After pressing the button, the heating element behind the rearview mirror glass will quickly heat up to a fixed temperature within a few minutes. The icon for the button-type rearview mirror heating switch needs to be distinguished from the front windshield defogging button. The front windshield defrost button is represented by a fan shape with three rising curved arrows inside, while the rearview mirror heating button is represented by a square frame with three rising curved arrows inside. In addition to button-type switches, some cars have a knob-type rearview mirror heating switch. On the driver's side door, there is a knob on the left front with several symbols: L, 0, R, and a heating symbol. The heating symbol, which is a square frame with three rising curved arrows inside, serves as the rearview mirror heating switch. Turning the knob to the heating symbol activates the rearview mirror heating function. Rearview mirror heating works by installing small heating wires inside the rearview mirror lens. When the driver activates the rearview mirror heating function, the heating wires quickly warm up to a fixed temperature, typically between 35-60 degrees Celsius, within a few minutes. This helps defog and defrost the mirror surface. The rearview mirror heating function is most commonly used during rainy, snowy, or foggy weather to ensure a clear mirror surface. Precautions for using the rearview mirror heating function: After turning on the rearview mirror heating function, the defogging or defrosting effect is not immediate. The frost or fog will gradually disappear after preheating. Excessive use of this function, especially for more than 30 minutes at a time, can affect the lifespan, clarity, and brightness of the rearview mirror. The rearview mirror heating function generally activates only when the external temperature is below 20 degrees Celsius. If the outside temperature is high, the rearview mirror will not heat up even if the switch is turned on. The rearview mirror heating function is designed to remove fog droplets and frost from the mirror surface but cannot eliminate raindrops in heavy rain. During heavy rain, the heat generated by the heating wires is insufficient to evaporate continuous raindrops, so the mirror surface may still become blurry, affecting the driver's visibility. Cars equipped with rearview mirror heating have special mirror lenses that differ from regular ones. Heating mirror lenses come with heating function connectors, so this must be taken into account when replacing rearview mirror lenses.
When I drove a BMW 3 Series before, I noticed that the rearview mirror heating function is usually integrated with the rear window defogger. That button is located on the climate control panel, typically featuring a square icon with wavy lines or a fog pattern. Simply activating the defogger button will automatically heat the mirrors, which is particularly useful for preventing fogging during rainy days or winter. To activate it, first ensure the engine is running - the system responds more easily when the climate control is in AUTO mode. Depending on the model year, the location might vary slightly: for example, older models place it on the left side of the dashboard, while newer versions may have quick settings in the central display menu. I'd recommend consulting the owner's manual or visiting a professional shop if unsure, because mirror clarity directly impacts reversing safety - don't tamper with the electrical system randomly.
