Car: 2004 RX330 with 87800 miles

All of a sudden, the rain sensing wipers on our 2004 RX330 do not work at all.

The manual mist, low and high settings work fine, but when the wipers are set to 'auto', the wipers never come on at all. We are getting a pretty good mist right now and they never came on while driving. The rear window wiper works fine in both intermittent, low and high.

The only thing I have done is change out the battery .... I broke out the manual, but no hints in there (I thought it might be like the power windows where you have to reset things).

I read a TSB and I am thinking the rain sensing tape may need to be replaced, but that is just a wild guess.

Any thoughts?

 

Try tapping on the sensor, see if the wiper go on.

 

was this during the light snow we had?
Mine had that same problem Saturday night during the heavier snow. Then on Sunday the auto wipers worked just fine from the over spray on the highway. I think the cause was that it was so cold that night that the top part of the windshield would freeze covering the sensor.

If that wasn't the problem then try covering the sensor and see if the wipers work.

 

Try cleaning the glass thoroughly and applying a product like Rain-X that encourages water to bead up on the glass. If it is sheeting off, it may not activate the sensor. As I understand it, the sensor fires a beam of IR light up through the glass (the sensor and IR lamp are contained in the mirror mount) and looks for backscatter caused by the presence of raindrops on the outside surface. If the drops are too fine or there are not enough of them to create a threshold level of backscatter (you set that threshold with the +- switch), you may not be triggering the wipers.

Sometimes I've noticed either that particular section of the windshield isn't getting large enough drops, or that the mist is too fine to detect. A quick coat of Rain-X will help water to bead - and also make the need for the wipers less critical.

 

This is how the Lexus rain sensing wiper works:

The auto wiper system operates when the wiper switch is in the AUTO position.
The rain sensor is connected to each ECU through the multiplex communication line.When the rain sensor detects raindrops in the detection area of the windshield glass, the sensor sends a wiper control signal according to the amount of raindrops to the windshield wiper relay assembly.
When the rain sensor malfunctions, DTC of multiplex communication systems can be seen at the same time.

The cause can be a blown fuse, loose harness/connector at the overhead junction block , a broken rain sensor circuit or rain sensor itself

I would take it to the dealer.

 

This was on Saturday during the light snow and also the heavier snow.

I am looking at the forecast and it appears as though it will warm up enough on Saturday to give the RX a bath, I will see if the wipers work then ... more to follow, thanks for all of the replies.

 

Disregard, they are working fine. Went through a car wash today with warmer temps and the auto sensing wipers worked great.

 

Still, this is a good learning episode for many who might experience something similar. While the final outcome may have been nothing and all is well in the end, we appreciate you taking the time to share your experience.

 

thats good to hear

 

Yes! Tapping makes the wipers cycle when the control is set to AUTO! I thought this was an infrared system. Why does tapping on the sensor box trigger the wipers??
The sensor seems to work very poorly...if at all. Worthless in drizzle. Can this be fixed?

 

I agree the Germans still have hands on the rain sensing wipers. At least Lexus lets you adjust the sensitivity.

 

Mine go on everytime I adjust the rearview mirror - it must move the sensor a little and off they go!

 

My guess is that tapping triggers the wipers because the fingers reflect some of the sensor signal back to the sensor, much like rain. You could probably just touch the glass and have the same result. Just a guess.