On most cars, the small switch or lever on the bottom edge of the rear-view mirror controls the auto-dimming glare reduction feature. Some mirrors also incorporate extra features like a HomeLink garage-door opener or a compass, but the dimming control is the most common function.
This article explains what the switch does, how auto-dimming works, and how to identify and use your specific mirror configuration.
How auto-dimming mirrors work and where the switch fits
Auto-dimming rear-view mirrors detect glare from headlights behind you and automatically darken the glass to reduce distraction. In many vehicles, a small lever or slider on the bottom edge lets you enable, disable, or override the feature. The exact control can vary by model, so consulting your owner’s manual can clarify your specific setup.
Common forms of the switch you might see
- Bottom-edge lever or small slider to enable or disable auto-dimming. In many cars, moving the lever toward "OFF" disables the feature; returning it to the auto position re-enables it.
- Manual dimming override to set a fixed darkness level in some models, useful in unusual lighting conditions.
- In some luxury or newer models, the mirror housing may also include other features (such as a HomeLink garage-door opener panel or a compass/temperature display) that are separate from the dimming switch.
In short: primarily, the switch is a glare-management control that lets you toggle auto-dimming on or off; other features may be present but are separate from the dimming control.
How to identify your mirror’s exact function
Because mirror features vary widely, use these steps to determine what your switch does:
- Look for a label or icon on or near the switch (sometimes a sun-like icon denotes dimming).
- Check the vehicle’s owner’s manual or trim package description for “auto-dimming rear-view mirror” or “mirror with HomeLink/compass.”
- Test the dimming: with the car on, shine a bright light behind you and observe whether the mirror darkens when the switch is in the auto position; toggle as needed.
Safety note: Polarized sunglasses can affect auto-dimming behavior in some situations; consult the manual for any caveats.
Summary
The switch on the rear-view mirror is usually a control for auto-dimming glare reduction, with occasional manual override options. Some mirrors also house additional features like a compass or garage-door opener; to know your exact configuration, refer to the owner's manual or vehicle specifications for your model year and trim.