2016 Honda Civic: Rain-Sensing Wipers Back in Business
by Dan Edmunds, Director of Vehicle Testing on January 27, 2017
Rain-sensing wipers are useful in Southern California, but we can go months at a time without the need for any sort of wipers at all. I know, cue the tiny violin.
This enviable atmospheric reality explains why we didn't immediately realize that the reason our 2016 Honda Civic's rain-sensing wipers didn't work during my rainy Thanksgiving road trip was linked to a windshield replacement carried out the previous July.
I eventually put two and two together after doing some internet sleuthing upon my return and was able to visually confirm that the rain sensor wasn't making proper contact with the windshield. Presumably, this was the result of a goof-up by the windshield installer.
So Mike Massey, our vehicle testing assistant, called Safelite, the company that did the original work. Our problem didn't sound wholly unfamiliar to them, and they happily agreed to send a mobile glass replacement truck to our location to sort it out.
The installer confirmed my tentative diagnosis and climbed inside the car to get at the sensor by removing the plastic shroud up behind the rearview mirror. Looking at it from outside, it seemed to me the sensor hadn't been properly snapped back into place. He discovered this was indeed the case, but it wasn't as simple as pressing it into place until it clicked home.
There's a silicone sheet between the sensor and the glass, and it has to make full contact so it doesn't disrupt the trajectory of the infrared light (IR) beams emitted by the sensor. Bubbles and tears create problems, too. That's because rain-sensing wiper systems work by projecting IR light into the windshield at an angle, where it bounces around within the glass until it comes back to a collector.
All of the light will return to the collector when the glass is dry, but the presence of water droplets will refract some of it away and thereby diminish the amount that returns. The effect is proportional to the amount of water, and this relationship allows rain-sensing wipers to automatically adjust their speed until full signal strength — the sign of a dry windshield — is restored.
Silicone sheets (also known as "silicone gel pads" by those in the windshield industry) come in all shapes and sizes, but the differences are small. Windshield installers carry an assortment with them, and they generally come from a third-party supplier. In our case the wrong part number was used, and the original installer didn't notice it wasn't making full contact after the sensor was refastened to the windshield.
Our technician figured this out fairly quickly and swapped in the correct silicone pad. After that he tested his work using a simple method: He turned the wipers to Auto and squirted water on the windshield with a spray bottle.
Wipe. Wipe, wipe. Wipe, wipe, wipe. Our Civic's rain-sensing wipers once again worked in proportion to the amount of moisture on the glass, as intended. They sensed rain, in other words.
A few days later I found myself back in the Civic as a barrage of storms was passing through Southern California. Wipe. Wipe, wipe. Wipe, wipe, wipe. I was easily able to confirm that they worked in the real world, too.
Dan Edmunds, Director of Vehicle Testing @ 19,324 miles