Before I start, I have a Fuyao aftermarket windshield. It has a bracket and spot for the sensor. They actually make windshields for BMW, but that don't mean much. I read yay and nay about aftermarket windshields, but it seems if the tape is replaced it should work.

When I got the car the auto wipers worked, but were very erratic. They would come on with no rain, or not come on in rain. It did pass a squirt bottle test with quite a bit of water. No tape was installed.

Ok, I got the OEM tape, installed it very carefully by the book "rolling" on the sensor so there are no air bubbles.Installed it back in the bracket.

It will pass a squirt bottle test with no problem, down to a few drops.

But, when driving, it seems that it needs a bit of rain to wipe. At 60Mph, in a light rain, there is a few second delay between wipes, there is definitely raindrop accumulation that would make you want to activate the wipers, but it does work. It also seems to make one wipe. I would think with that amount of rain, it would do two or three. Seems like if it were a standard intermittent wiper, it would be on the lowest setting. At rest with the squirt bottle, seems they would be long triggered with that amount of rain.

One time it seemed to be working correctly, then it stopped.

Does it need a calibration period? I didn't read anything about it. Is that the normal way it works? Seems like it needs to be more sensitive. I played with the settings on the stalk too.

 

My LS wipers display this kind of behavior even with the OEM windshield. Sometimes I have to manually click the stalk to clear the window which is very annoying but then the wipers seem to kick into action.

 

The day afterwards I drove in another rain, maybe a bit heavier, and they worked somewhat better. Maybe Ambient light affects it too. I guess it is a good feature if some car splashes off your windshield when you drive. No reason not to leave it on. I'm thinking Aerodynamics and wind can also push water away from parts of the windshield. I may try rainx too.

 

I'll note another thing I forgot to mention. At a light, I saw a toyota behind me, and the wipers pretty much were working the same way. They certainly work, but they seemed like they needed some coffee.

 

Hi gs350fan,

Lol… mine seem to have a mind of their own. Just as sha4000 above, often I check to see what mode the switch is in because they don’t turn on when I think they should once it starts to rain. If I manually bump them on, then from that point forward they work as they should. They have also turned on with basically a dry windshield; this pisses me off more than not turning on when it’s wet. Nothing like a couple drops of water and a dirty windshield then poof, suddenly you can’t see s***!

I wouldn’t worry about it working erratic, could be a number of factors involved.

What’s more troubling is an erratic sensor in a self driving car!

 

Yeah, a few stray drops today activated it. It should not have gone on, but it is proof it does work. Also, if you touch the sensor it will activate. This changes the angle of the light slightly. It is certainly based on the principle of total internal reflection. That is how fiber optic cables work. I've never seen it go on so far in the dry.

https://en.wikipedia.org/wiki/Total_internal_reflection