larryssf

I have had a couple of incidents where my rain sensing wipers were activated when it was not raining. Today, I actually had to turn the wipers to the "off" position to halt the wipers.

Have any of you had this experience. My forum search did not locate any similiar stories. Today I received by J D Powers questionaire for Initial Quality Study. This issue may have to added.

The wipers are quite (unlike some others), but I don't want them to operate in the sun.

pa28pilot

I don't usually turn them on except when there's visible moisture. (I think there's a warning in the manual about running them dry.)

That having been said, I have found them to quite adequately modulate the wipers. On days when it has rained and stopped, the wipers have all but shut off completely.

johna1

I've had a couple of times where this has happened, when the windshield is dirty, especially dusty. I guess the sensors just know there's something there, not necessarily water. Depending on my mood, I either turn them off or squirt the washer.

I think it would be a bit rough to downgrade the quality survey for something like this. Unless, of course, it is just a faulty sensor or something, in which case go for it!

reaxion

The "auto" feature if for when there is actually rain and you want the rain sensor to control the frequency of wiping.

Its not designed to be left on all the time.

The rain sensors dont actually detect rain, but rather reflections from the rain droplets. Apparently, in hot weather, certain reflections can trigger the wipers to wipe.. if left in the AUTO mode.

Well, atleast this is what i've been told by the technician.

ATS

Well that makes sense, there isn't a "moisture" sensor most likely a reflection sensor.

steph280

Those damn birds!

prprandall51

The sensor consists of a transmitter and receiver (infra-red, I think). The transmitter sends a beam of light out through the glass that is reflected back of the front "skin" of the glass into the receiver (remember light in prisms in scool physics?). On the MB, it looks like there is a bank of transmitters and receivers for more accurate assessment of the rain "situation". When the glass is clear of rain drops, all of the light beam is reflected back; when it rains, the droplets of water on the front skin of the glass effectively destroy the nice flat reflecting surface by making it "bubbly". In this situation, very little of the light makes it back to the recievers as most of it is scattered by the curved inner surface of the rain drop and so a signal is sent to the wipers to give a sweep. If more droplets fall, etc. etc.
I think the most likely cause of incorrect swipes would be stray light entering at the correct angle to be picked up by the receivers; for screen contamination to trigger the wipers, it would really have to be something that "bonded" to the windscreen in the same way as water does (such as tree sap, as I have found)

Barry45RPM

Use this feature only when it is raining/drizeling. If you leave it on all the time (like the auto headlights on feature) & you go to a car wash, they will turn on and, what will come out the other end of the car wash will be expensive to repair!