How auto-dimming rearview mirrors work

Rear view mirrors are items that currently offer technologies such as Wi-Fi connectivity, Bluetooth, reversing cameras, touch screens, and auto-dimming. The latter is of great importance for drivers who are sensitive to the headlights of other vehicles, and here we will explain how it works.

Auto-dimming mirrors are offered on many modern vehicles today, and have actually been around for a while. It's a subtle feature that doesn't stand out, and you might not even notice it's there. Auto-dimming mirrors are more common than they used to be, but they are still not standard on all models.

Magic mirror? No, electrochromism

If you never need to flip a switch in your car to easily switch from day to night, chances are you have an electrochromic rear view mirror. Electrochromism refers to the change in color of a substance that occurs when an electric current is applied. 

How do auto-dimming rearview mirrors work?

When light sensors in the mirror pick up glare, current is directed to an electrochromic gel that sits between two pieces of glass in the mirror. This current causes the gel to change color, which darkens the appearance of the mirror. When there is no more glare to activate the sensor, the current stops. The color change is then reversed and the mirror returns to normal.

There are various options for auto-dimming mirrors. Some of these include a built-in HomeLink wireless control system that lets you control garage doors, gates, home security systems, and even lights and appliances.

Should you buy auto-dimming mirrors?

Depends on. Unless you're photophobic (sensitive or intolerant of light) and are content to simply flip the little latch on your standard rearview mirror, an auto-dimming mirror doesn't have to be on your list of must-haves.

But if your eyes are more sensitive to light at night than during the day, or you just don't want to fiddle with a mirror while driving on the highway, an auto-dimmer might be worth it. They're standard on many premium trims these days, so your next car might be ready to protect your eyes from glare.

Do you have auto-dimming side mirrors?

Yes, some automakers offer complete auto-dimming mirror systems (side and rear view mirrors), but not all. Many of these companies only offer auto-dimming technology on the driver's side mirror. This is confusing as drivers have to check both mirrors for safety, and other drivers on either side can just as easily blind you when driving down the road.

Can I install an auto-dimming mirror myself?

Technically, anything can be done in the car, including new auto-dimming mirrors. You can buy OEM (Original Equipment Manufacturer) auto-dimming mirrors or buy an aftermarket model that works with your car. The advantage of doing it yourself is that you will save money and get exactly what you want. Bad news? This is time consuming, you have to get used to connecting the power and you can damage your windshield if something goes wrong. 

If you are inexperienced with DIY cars or haven't done it before, it's probably best to get this done by your local service department. You will have to pay for the work in addition to the cost of the product, but this can be fully justified.

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