I recently "adopted" my mother's 2008 RX350 for a very fair price. Today was the first day we've had rain since I brought the car home. I gave my husband my 2007 RX350, so I am very accustomed to the rain sensor wipers. This morning they did not go on, so I pushed the lever all the way up to clear the mist and then moved the lever two down to the "auto" position. The wipers started doing their thing, but after one swipe, they were going like gangbusters, as if I was in a torrential downpour, but I was just at a stop sign experiencing a light drizzle. Super overkill. I was afraid they were going to break and fling off the front of the car. I tried the other manual speeds and they did slow down, but every option went the same speed and the interval timing dial didn't change a thing.

Can anyone tip me off to what is going on? I'd rather have a go at a fix myself rather than fork over $$$ at the dealership.

Thanks

 

Do the wiper sensors on this gen Lexus use the same setup as the newer ones? I had a 2013 ES, and when the rain sensor stopped working properly, the dealer had to replace a gel pack in the sensor(the gel dries out), which I guess is how it senses rain drops. It cost 100 bucks to get it done. May be a similar issue with yours.

 

There is a control module called the "Auto Wiper ECU" that runs the wipers. Since all the different switch settings seem to not work correctly, I suspect the ECU. Perhaps you could swap it with the one in your 07 RX to see. It is located under the dash in the area above the glove box.

 

Sometimes dirt or mist seems to cover the sensor even after the windshield gets wiped, in which case my wipers keep running. I usually just hit it with washer fluid and it calms down. Sounds like your problem is more extreme though.

 

Might the windshield have been replaced? The sensor may have been replaced, mounted or connected incorrectly
or is now obstructed by some of the upper edge masking design.

 

Excellent Idea. I'll try that in a few days when I have enough time. Thanks!

 

I'll have to ask if they ever had it replaced. They bought it from a Lexus dealership, so you would hope they got that right. I don't know if they ever had replaced since then.

 

I took out the glove box and retrieved the Auto Wiper ECU. I did the same to my husband's car and actually switched modules. His car continued to operate normally, even though he wasn't too pleased with my watering down his car to simulate rain! My car had the same issues as before, leading me to think it is the sensor in the windshield.

Any thoughts?

I took some footage to show how I got in there. Sorry, I'm not a great videographer.

https://drive.google.com/file/d/1c3O...ew?usp=sharing
https://drive.google.com/file/d/1XnJ...ew?usp=sharing

 

¯\_(ツ)_/¯.

 

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I'll have to ask if they ever had it replaced. They bought it from a Lexus dealership, so you would hope they got that right. I don't know if they ever had replaced since then.

 

Thanks to your video, I was able to find the wiper ECU in the parts book. The parts book shows it behind the speedometer cluster (expletive deleted). But it only created confusion for me. Your video showed part number 85940-48030. When I ran that number on the 2007 listing, it came back as not for 2007. The 2007 uses part number 85940-48010. Yet functionally they seem to be the same.

I don't know what to suggest next. The rain sensor on the windshield is glued on, so you can't swap it with your other car. Personally, I don't think that is the problem, but then my track record so far isn't that great.

That leaves the windshield wiper switch itself. The part numbers for the 2 years are the same, but both cars have to have or not have the telescoping steering column. It is a replaceable item, so you could swap the switch between cars. I have never done it, so I can't say how easy/difficult it would be. Other than you have to take the plastic cover off of the steering column, I'm not sure how the switch is attached. On other cars it is just a couple of screws, but this is a toyota. Here is a link to a photo of the switch - https://www.rockauto.com/info/903/1S10073__ra_p.jpg

 

I would just take it in and get it properly diagnosed.

 

I realize this is an older thread so you may have solved the problem, but I actually had the same issue with my RX330. My car acted the same way for years, and it turns out the sensor was not fully clipped into the bracket on the windshield! I had to slide the clip as shown at 1:30 in the linked video to unlatch it and I clipped it fully back into the bracket. My rain sensing wipers have worked perfectly since!

 

Thanks for posting the video. I always appreciate people posting things that teach me how to access parts of the car.

This is a FYI for others that read this thread and watch the video. What I realized as I watched the video is that Lexus changed the rain sensor mounting. On my 2007 RX350, the rain sensor "block" is mounted dead center behind the mirror, not off to the side like your 330. It is also shaped a little different, but I did not try to remove it to see if the insides were the same. Also, the console on the roof over the mirror is also different on the 350.

 

Oh, sorry! I should have specified that that specific video is actually for the GX470! My RX330 is set up the way you described! I reattached the sensor a couple of years ago so my memory is a bit hazy, but I do remember the clip sliding out and the sensor pulling away from the windshield in the same manner.