You have to " initiate" it to start by moving the wiper stalk." Once initiated it will make a sweep (double on my car). It will then "wait" for enough precipitation to fall on windscreen to initiate another sweep...
Have someone provide "rain" with a hose set on shower.., then initiate and see what happens....
Try the method noted above. If fails, look at the windshield - the sensor is built into it. Have you had the windshield replaced? I had this problem after windshield replacement and they replaced at no charge and all fine now.
Definitely sounds like the sensor to me. On the outside in the middle right at the rear view mirror is the sensor. If you see a lot of air bubbles or glue, the sensor likely came away. Only fix is windshield replacement.
I'm curious about this issue as well. A few months ago I had my windshield replaced, the rain sensor function quit working and the glass shop replaced the rain sensor but to no avail. They said "the dealer would have to program it". Is this a true statement? Is this a DIY programming job?
While you can replace just the rain sensor, don't do it - the adhesive used can create air bubbles and other interference that prevents the rain sensor from sensing water drops. With a new windshield, the sensor always comes factory attached. You need to tell your glass company to replace the entire windshield with new sensor.
Interesting. Yesterday was the first time that I got caught in the rain with my new to me Z and the first time turning on the wipers. I have had several cars in the past that had rain sensors and they NEVER worked properly. I always wished I had delayed wipers rather than sensors. Well, the sensor on the Z actually worked exactly the way it is supposed to, and I am just about positive the windshield on my car was replaced (it says Pilkington on it and it has absolutely no pitting, so I'm guessing it is fairly new.) I am happy with the functionality of the sensor.
I had mine replaced too with a Pilkington. The first replacement had a faulty sensor, however, windshield company promptly replaced and that one works perfectly. The point is, must replace entire windshield and not just sensor.
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