Automatic wipers

[nigel4]

How do the automatic wipers work (what are they detecting)?
How well do they work?
Are they affected by car wash residues, wax or ceramic?

 

[Alb]

The sensor detects spots of water on the windscreen.

 

[MikeJS]

Mine work very well and I have a ceramic treatment on the glass which does not seem to degrade the wipers in any way.

 

[KnightRider]

They work on a curious bit of physics...there's a led and a receiver. Normally light from the led doesn't get to the receiver but when it rains...the water/glass interface changes this...nice

 

[markp4200]

I have found them better then on previous cars I have owned - no issue at all.