2005 S-Type 3.0

This is just a question to satisfy my curiosity....

How do they work? I've had mornings when the dew or remains of a storm was all over the windscreen but they didn't turn on. Other times the least drizzle will cause a wipe....or even three or four.

An inquiring mind wants to know.

Eric

 

My stock answer is "they don't work very well"....

I'm talking about this feature on ANY car. We don't have it on our S-Type, and I'm glad that we don't. We do have this feature on my wife's 2004 Lexus RX330 AWD, and the operation is just as you describe it - erratic and unpredictable and completely oblivious to the amount of water on the windshield.

I'd much rather make the decision myself as to when to turn the wipers on and off. Plus, it's one less array of costly electronics to screw up and break down....

 

My sense is that the sensor for them is not in an obvious location such that dew on the windscreen doesn't produce an action. However, I can't guess where the sensor is.

Eric

 

I think it's a shock sensor, not a moisture sensor. As for the location, I think it's built into the rear view mirror mount. When a rain drop hits the windshield, the sensor feels it and turns on the wipers.

 

I also found this:

A new type of wiper system is starting to appear on cars that actually does a good job of detecting the amount of water on the windshield and controlling the wipers. One such system is made by TRW Inc. They use optical sensors to detect the moisture. The sensor is mounted in contact with the inside of the windshield, near the rearview mirror.

The sensor projects infrared light into the windshield at a 45-degree angle. If the glass is dry, most of this light is reflected back into the sensor by the front of the windshield. If water droplets are on the glass, they reflect the light in different directions -- the wetter the glass, the less light makes it back into the sensor.

The electronics and software in the sensor turn on the wipers when the amount of light reflected onto the sensor decreases to a preset level. The software sets the speed of the wipers based on how fast the moisture builds up between wipes. It can operate the wipers at any speed. The system adjusts the speed as often as necessary to match with the rate of moisture accumulation.

I'm not sure which kind our windshields have. It's either the vibration sensor or the light sensor. They have both types.

 

I'll check the area of the mirror mount. I have an unusual car because I have the electric windshield defroster. That may be impacting the operation of a shock sensor. Don't think it should but maybe....

Thanks.

Eric

 

It's NOT a shock sensor. It is optical like what was described above. You must get the correct windshield replacement because the cars without automatic wipers don't have this "special" spot in the windshield. It's a patch that is centered on the rear view mirror. Without it no automatic wipers!
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