Dimwitted auto wipers

[Declan C]

Hi all, does anyone else find the auto wipers a bit daft? For example:

 

1. On starting the car with a wet windscreen, they don't wipe until you manually tell them to, even if they're already in auto mode.

 

2. Sometimes they just randomly start intermittently wiping a dry screen?!

 

I guess they generally work "ok" but they just seem to be a bit silly! Is this common experience or does it suggest a fault with a sensor?

[ALSALPHARD]

Hi we had a new winscreen on our Auris and fitter didnt put some gel between sensor and screen, = meant didnt work properly. The  second fitter came along put some in and voila working fine now, so maybe gel degrading but just a maybe!

[big_boz]

20 hours ago, ALSALPHARD said:

Hi we had a new winscreen on our Auris and fitter didnt put some gel between sensor and screen, = meant didnt work properly. The  second fitter came along put some in and voila working fine now, so maybe gel degrading but just a maybe!

I had something very similar in a Volvo years ago

[jpiech]

I haven't noticed them coming on when it's dry but I definitely noticed they won't start when the windscreen is already wet and I have to do it manually.

It is strange.

[Geralt]

I have an idea why it only works when you activate the wipers.

 

The sensors work on changes in light reflection. So I'm guessing that since there's an infinite set of light and cleanliness conditions it's not possible to calibrate the device at the factory for a dry windscreen. The only way the system can be sure that the windscreen is dry (in the current lighting conditions) is just after you've activated the wipers. Thereafter, it's a safe bet that any abrupt change in light reflection is most likely due to rain...usually.