1997 PA Rain Sensing Wipers

[nrvespa]

This really isn't a post for how to fix something, but rather how something works. I've had my PA for a little over a year and I have the rain sensing wipers (BTW I love it). My questions are -- How do they work? What triggers the wipers to speed up/slow down? How do they know not to work when its not raining?(Sometimes a few days after a rain, I realize that they are still on)

I see the little box next to the mirror, but I cannot figure out how it affects the wipers. Anyway, Im just curious.

[tman]

It's magic stupid!

kidding of course! THe little box next to the mirror had light sensors in it. Then rainwater is above this sensor, the sunlight gets refracted, making rainbow patterns, which are picked up by the light sensor, and it triggers the wipers based on how much refracted light there is.

This is my theory, not sure if its true, but its how I've assumed it works.

[HotZ28]

You’re pretty close T-man! The link below gives full details;
http://auto.howstuffworks.com/wiper4.htm

[tman]

See, and they told me I'd never amount to anything....

[nrvespa]

Thanks guys...very interesting. Now I have knowledge on one more thing in life.

-NV

[TopherS]

Originally Posted by nrvespa

What triggers the wipers to speed up/slow down?

As mentioned in the link provided by HotZ28, the harder it rains, the less that the windshield stays clear after the wipe cycle and it triggers the wipers to wipe again. But if you find that it is being too (or not enough) sensitive, you can turn down (or up) the sensitivity by adjusting the delay settings. For mine, I find that the middle (3rd) setting usually provides the best interval, if I go even one more click sensitive, it seems that they are constantly wiping, even in just a mist.

I was just reading last week about some road test drivers complaining of the system being "thrown off" or confused by passing trucks or overpasses. I never have found that to be a problem with mine, but maybe they weren't familiar with how the system works. Who knows...?

Originally Posted by nrvespa

I see the little box next to the mirror,

I always wondered what that was on the Park Ave's and Cadillacs...I thought it might be for the compass in the mirror. Mine is different, though, it's mounted down below the mirror, rather than off to the side...and there's a large built-in plastic cover from the mirror to the sensor.

I, too, love this feature...especially in the rainy Pacific Northwest. In the winter, I can go days, sometimes weeks and never shut the system off. Just goes to show how great these cars are...auto windshield wipers, auto headlamps, auto climate control, auto dimming mirrors...these cars practically drive themselves, just point it in the direction you want to go.

By the way, there is an aftermarket system that you can install on your car if it doesn't already have it. It's called Raintracker. They have their own website, which has pretty detailed online instructions on how to install the system on any particular vehicle. I have also found the system for sale on eBay. I'm going to get one for my wife's Rendezvous (if she'll let me ).

[imidazol97]

The sensor relies on the fact that if there is little difference in the refractive properties of the glass and the water on the outside and the infrared light is not reflected at the contact surface and leaves the glass. That causes the wipers to operate. If there's an oil layer on the outside of the glass it also seems to pass the light on through out of the glass. That oil can be removed with SOS pads in my case. You can use oxalic acid in Barkeeper's Friend also. Then the sensor won't be fooled by the streaking with a little mist acting like more water on the sensor area.

[rwalters_pctech]

I have a question. I had a new windshield installed and they said the rain sensor can't be re-used. It looks like it's only stuck to the windshield with some adhesive. What gives?

[HotZ28]

Who ever told you that, is FOS! Get a second, (or third) opinion!

[tman]

Yeah somebody is jerking you around, go somewhere else to have the windshield replaced

[rwalters_pctech]

Well good news! You guys were right. I told the Glass shop not to order the $90.00 rain sensor and just leave my original sensor on the seat. I got home, cleaned all the old glue off of it and then glued it right back on. Works perfectly.

[Loekee75]

Goes to show that some people will do anything for a buck! It's pretty pathetic.