I replaced a windscreen for an Audi dealer, however, there was nothing wrong with the glass. I asked what the change was for, and it was pointed out that there was an issue with the automatic rain and light sensor. So why was the windscreen cited as the issue?
In his report, the investigating Audi technician concluded that the sensor was not functioning due to the car having a non-genuine windscreen replacement; the (aftermarket screen in it was made by AGC Automotive). As the car was to be sold whilst still under manufacturer warranty the investigation ended there, and could not be resumed until a genuine, Audi branded glass was in place. I duly obliged. However, shortly into the strip-down I discovered what the cause of the issue really was: a damaged rain sensor. The previous installer had damaged the circuit board inside (there were screwdriver marks in the casing).
The car in question was registered in 2016, so much of its warranty would have still been in place; just as long as any parts replaced were authentic, Audi branded.
Another similar situation unfolded when a Volkswagen main agent was investigating a sensitivity issue on a rain sensor on a fairly new Golf; the owner said the automatic wipers didn’t seem to react as well as he though they should. The VW technician noted the windscreen, an aftermarket version by Saint Gobain (Sekurit) and quickly surmised that it was the cause of the problem. I went along to give a second opinion.
The first place to look for obvious things that could be wrong with a poorly functioning rain sensor is the rain sensor module. I removed the rear view mirror assembly and immediately saw that the rain sensor was not seated properly in the mounting bracket. A push and a click later, the wiper sensitivity was restored to optimum level. However, VW did tell the Golf owner that if there was an issue with the rain sensor (or windscreen) whilst the car was under manufacturer warranty, it would not be covered owing to the non-genuine windscreen in the car.
Whilst these examples may seem excessive, windscreens can be much more complex than the two highlighted here. With radio antennae; heater elements; GPS hardware; Lane Departure Warning sensors; Autonomous Braking hardware; Head Up Display and more, the windscreen is no longer just a piece of glass shielding the car’s occupants from wind and flies. The best available parts, especially if the car is still under warranty (or the more technology connected to the glass) will always be what the vehicle manufacturer endorses.