What is a Windshield Rain Sensor?

If your car or SUV is equipped with a rain sensor, it will automatically activate your windshield wipers.  It’s a great feature to have on your car and very important to discuss when you are about to schedule a windshield replacement.  If you’re not sure if you have one – you might have this feature and not be aware of it – we’ll be happy to walk you through how to make the determination.  A few months ago, I spoke with a gentleman who needed a new windshield for his 10-year-old BMW – a 535i xDrive. When I asked if he had this option, he said absolutely not!  He went on to say he has had the car for ten years and he drives over 20,000 miles each year. If he had it, he’d know!   You can guess the rest of the story, right?  We scheduled the appointment and went out with the wrong windshield.  It wasn’t a problem, we just went back with the correct windshield and replaced his windshield.  We make every attempt to arrive with the correct replacement parts on our first visit.  The best way for us to do this is to get your VIN (vehicle identification number).  With the VIN, we are able to get the data directly from the vehicle manufacturer to find out exactly what your car is equipped with and the specific parts needed to do the job.

There are many different techniques that automakers have experimented with to eliminate or substitute the wiper system. A rain sensor is a fairly recent addition to the windshield of a car. The technology has been around since the 50’s, however, rain sensors didn’t become prevalent in cars until the late 1990’s.  Today, they are fairly common in domestic and foreign passenger vehicles and trucks.  A rain sensor detects the presence of water on the glass of the windshield. The sensor then prompts the car to turn on the wipers automatically whenever rain is detected.

What is the mechanism behind the rain sensor?

The rain sensor is mounted beside the rearview mirror in such a way that it is in contact with the windshield. A small portion of the windshield is blackened to hide the rain sensor. However, there is a tiny view port which is not blackened and through which the sensor is able to detect rain.  When you call us, we’ll direct you to this area on your car and help you to understand whether or not your car has this option.  Again, we can also get this information from your VIN.  We’re happy to help you in either case.

The rain sensor works on the principle of total internal reflection. This technique makes use of infrared radiation. An infrared light beams at a 45-degree angle on a clear area of the windshield from the sensor inside the car. When it rains, the wet glass causes the light to scatter and lesser amount of light gets reflected back to the sensor. When the amount of light reflected back reduces to a level preset by the software inside the sensor, it automatically switches on the wiping mechanism of the car to start the drying process.

The software also determines the speed of the wipers depending on the amount of moisture accumulation. This speed changes according to the detection of moisture by the sensor.

What is the benefit of having a rain sensor?

It is very important for the windshield to be clear while you are driving not just for your own safety but for the safety of other people or vehicles around you. The visibility level decreases to a large extent when it rains. The wipers need to be turned on immediately to clear the windshield. The rain sensor detects rain and switches the wipers on so that you are not distracted with the effort of manually engaging the wipers. This helps you to have better control of the car and ultimately – stay safe.

Installing and Replacing a Rain Sensor

In order to detect whether your car has a rain sensor or not, you can pay attention the next time it rains and sees if the wipers are getting switched on automatically or not. Rain sensor gel pads need to be replaced each time we perform a windshield replacement. If you’re not sure if your vehicle is equipped with a rain sensor, look at the photos below and if you still aren’t sure, just give us a call and we’ll help you. If all you need is a windshield repair from a stone chip or some other object making contact with your windshield, you will not need a new rain sensor gel pad.

As always, feel free to reach out to us by phone or email.  Telephone 610-935-5588 or info@trueblueautoglass.com.

Thanks for reading!

Scott

Examples of rain sensor buttons on Chevrolet, Ford, Lexus, Volvo and BMW vehicles.