I've noticed when the wipers are set to auto & at the highest sensitivity, they don't come on frequent enough. There's plenty of rain on the windshield but the wipers don't come on quick enough. I'm gonna take in to have Lexus take a look at it but wanted to see if anyone has any feedback.

 

Which way did u have it turned?

 

The sensitivity **** was turned towards me, down to the + sign.

 

Locate where the sensor is, and check to see if it's clogged up with dirt or car wax?

 

Any idea where the sensor is?

 

if i remember correctly, the sensor should be at the top near the mirror, should be a panel you can see from the outside

never had trouble with my wipers, but usually wipe down the windshield before i drive

 

yes, you can see frmo outside, area where the rear view mirror is "stuck" to the windshield

fwiw, i am never a fan of the stock sensor system neither. it's never really accurate. when i want it fast, it doesn't work. when i want it slow, light drizzle triggers it

my bmw works far better

 

Interesting tidbit mined out of google about how they work that could give you some clues about why yours aren't responding well:

The technology behind rain-sensing wipers is not complicated. A small area of the front windshield glass (usually located on the outside of the vehicle, opposite the rear-view mirror) is monitored by an optical sensor. The sensor is designed to project harmless infrared light at the windshield at an angle and then read the amount of light that is reflected back. A clean windshield will reflect nearly all of the light back, while a wet or dirty windshield will cause the light to scatter. The optical sensor can determine the necessary frequency and speed of the windshield wipers by monitoring the amount of light reflected back into the sensor.

 

Might make more sense to have two sensors and take the average. That may help with the windshield wiper frequency accuracy.

 

The rain sensor not only senses rain, it is speed depended as well. If you are at a red light, it will slow down or stop, if you are on the highway, it will go faster.

 

thanks for the info, that's good to know it's speed depended.

 

Interesting. I always thought the sensors are based on conductivity, which changes with wet surface. There actually seems to be two different technologies: electrical conductivity sensor and the infrared optical sensor. Does anyone know which one Lexus is using?

See below description of the other conductivity sensor:

" The rain sensor system comprises first and second electrical conductors spaced uniformly from one another and an electrical insulator interposed therebetween. A dual network voltage divider circuit couples the first conductor to an applied reference DC voltage level, and the second conductor is coupled to ground potential via a similar network. Airborne raindrops and moisture temporarily adhere to the exposed surfaces of the insulator to electrically couple the exposed surfaces of the first and second conductive surfaces to lower the electrical resistance therebetween. The magnitude of the applied voltage changes in relation to the intensity of rainfall or amount of raindrops adhering to the conductors to affect the rate of windshield wiper action. An rpm speed linearizing circuit may also be employed to compensate the rate of windshield wiper action in response to vehicle speed. The conductor has an elongated shape for providing self-clearing of raindrops or moisture from the sensor. "

 

Lexus use the infrared type. The conductivity type would only work if the two conductors are outside the windshield. I dont think any manufacturer us the conductivity type.

 

I have the similar problem from time to times.

 

I have noticed the same thing with my car. I will driving with the windshield covered and no wipers. I think it waits until visibility is mildly affected then it turns on. It wont turn on for a few droplets