What is a rain sensor in a car?

Michael Rogers
3 min readJul 12, 2021

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A rain sensor in a car detects any rainfall or moisture that makes contact with the windscreen and automatically adjusts their wiper movement accordingly.

The rain sensors assist in the ongoing battle against driver distraction. The rain sensor appears to be attached to the car glass behind the windscreen and behind the rearview mirror.

Rain sensor on a windscreen

Why do we need a rain sensor?

We’ve all been there before.

You’re driving down the road, it’s cold outside, maybe rainy or snowy too…

…and to add salt to the wound, mist starts to form over the windscreen and distorts your vision!

Windscreen fogging has always been a problem for drivers throughout the years. However, window condensation sensors are working on making window fogging a thing of the past.

How does a rain sensor function?

A condensation sensor is a small mechanism that watches the windscreen and is designed to sense moisture and condensation on the windscreen. If its sensors are tripped or alerted, then it works with the car’s ventilation system to redirect the flow of air. This ensures that the driver has optimal visibility when it comes to condensation based fogging.

This is also relevant during a windscreen replacement

There are a few ways to tell whether or not your car is equipped with this particular sensor. If the wipers start to work automatically when it’s raining or if you notice a change in airflow that you didn’t trigger yourself, chances are; your car is equipped with a sensor.

Windscreen while driving in the rain

Where is the rain sensor located on my windscreen?

This sensor is usually found on newer model cars, and it can easily be located behind the rearview mirror, which is essentially attached to the windscreen itself.

It is usually a discrete, square-shaped panel that’s rather small and it may even go unnoticed by you for years. Sometimes this rain sensor is found next to a light sensor which triggers the headlights if the lighting outside is too low for ideal visibility.

To tell if you have a light sensor, your lights will turn on automatically if you start to drive in darkened conditions and it is usually mounted behind the rearview mirror all along with the rain sensor.

These two sensors work together to make sure that you can see your way home no matter what conditions you find yourself in.

Car with rain sensor driving in rain

Which car will always have a rain sensor?

Mercedes-Benz has always been a name associated with quality, luxury and safety when it comes to higher-end vehicles. Among their newest innovations is something called a rain-sensing wiper.

The rain-sensing windscreen wiper is a safety feature that comes standard in a variety of Mercedes-Benz. Instead of having to switch the windscreen wipers on yourself in the event of rain or snow or other precipitation, the rain-sensing windscreen wipers will handle this for you.

Rain sensor close up image

How does this increase my safety?

Rain and snow another precipitation change based on the severity of the weather. What starts out as a drizzle could become a full-blown thunderstorm in a matter of minutes.

Drivers have had to deal with keeping an eye on the speed and frequency of their windscreen wipers. If not used optimally, this could create unneeded wear and tear on the machine.

These rain-sensing windscreen wipers automatically adjust their activity according to the outside requirements. The rain sensors contribute to the ongoing battle against driver distraction. And that’s one less thing to distract them from their job of keeping themselves and everyone on the road safe.

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Michael Rogers
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I am here to share insights and knowledge that I have gathered over the 20+ years in the car glass and windscreen replacement industry.