OK, so for the past year I've battled with this darned metal bracket that the rain sensor clips to. For whatever reason I can't get it to stay attached to the windshield.
I've tried in order: two types of double stick tape, crazy glue, RTV glue, two different epoxy's, and lastly rear view mirror adhesive.

After a short time the bracket comes off the windshield and just hangs there. I scrape everything off the bracket and windshield. Clean it with alchohol. Rinse and repeat.

I can't prove it, but I swear last week when I got in the car, and noticed it hanging there is was laughing at me saying "try again sucker".

Granted the hot sun doesn't help, but still it's not like these things are falling off all over the place in hot weather.

Is there some special adhesive I should be trying that I'm just not thinking of? Also, I'm not talking about the clear rubber part (that they call tape for some odd reason). It's the bracket itself as below.

 

I would call a local long-time-in-business, well-respected indie automotive glass shop and ask them what adhesive they would recommend. And if they quoted me a fair price, I would probably let them do the job so I could avoid having to repeat this fix again and again.

 

Thanks RX. That's great suggestion actually.
The whole thing seems like it should be so simple that I've just been hell bent on DIY'ing it. Never really gave much thought to a glass shop. I could only think "dealer", and I'm not much impressed with the service dept of my local Lexus dealer so that was not an option. I'll find a glass shop and make some calls. I can't imagine much of a cost

 

Lets us know what the glass co uses. In reading the lexus manual, it talks about the using rain sensor tape (double sided sticky gel tape) - which is trimmed to fit viewing window of sensor - which is the same size as the inside rectangle shape of the sensor metal mounting bracket. It doesn't mention how the metal bracket is fastened/bonded to window glass.

 

Yes, if I get to know what they use I'll defintely pass it along. I have no idea who decided to name that gel "tape", but regardless, from what I know it's more to help the sensor detect the rain.
I replaced the gel months ago just for the fun of it Figured I have this thing on and off enough I might as well

 

Finally got around to visiting the auto glass shop (life's been busy). I told them what I needed, and one of the guys took a look, went back inside, and came out with a small bottle of Equalizer Black Moulding Adhesive.

He applied it to the rain sensor mount and put it back on. It's being held in place for 24 hours with some painters tape. I'll put the sensor back on tomorrow and we'll see how it goes.
Took him less than five minutes altogether. They didn't charge me anything, but I gave the guy some cash anyway.

Here's a link to what he used https://equalizer.com/black-moulding-adhesive

 

Good luck and let us know if that stuff works for you.

 

Thank you for the update

 

Short update just in case someone else has the same problem some day.

Everything held fine up until around June/July this year when the temps were in the high 90's. Got it the car one day and the sensor was hanging.

Purchased a tube of the stuff mentioned above and re-attached the bracket. I figured I got about 7 months out of it so not too bad I guess.

Got into the car this morning and it was hanging again Temps have been in the low 20's the past couple of days.

So, it seems I'm getting 6 months or so each time until we get some extreme temps.

 

I had good luck with Permatex rear view mirror glue in the past for the review mirror metal supports that fell off the windshields in some of my old cars.

Maybe this type of glue will work. Just be sure to properly clean the area and the part of any remaining old glue residue first before applying it.

 

Thanks! I did actually try that twice in the past. Held well, but only for a couple of months.

I'm considering tryihng an Oven Heat Resistant glue. It's supposed to be good for up to +300C, and down to -60C
Something like this

 

Weird. I used that Peramtex windshield adhesive on rear view mirrors that held for years until traded the cars that it was used on. The adhesive lasted even on hot Georgia summer days.

I would perform a proper clearing of the area before using any more glues. You may have to scrap the area clean of old adhesive residue with an razor(plastic or metal)and use alcohol to ensure that the area is oil-free before applying whatever glue you are using to ensure a proper adhesion. I have learned that you must perform proper prep work of the area and part for any glues to make a successful permanent bond.

Take some pics of the windshield area and the part after you cleaned it before you apply any glue to it.

 

I've used the Permatex many times over the years for rearview mirrors, and it's always worked great for those.
Yep, I've scrapped both the window and bracket clean. Wiped clean both with rubbing alcohol each and every time.

I'll try and remember to grab some pictures first

 

Noticed that you've mentioned scraping and alcohol cleaning surfaces but not sanding. Permatex rear view glue kits I've used come with sand paper to rough up glass and metal surfaces which increases surface area and adhesion. As a suggestion I'd also apply some pressure for several hours to the metal tab while glue is setting using a stick of wood cut to length or a screw type shower curtain propped up from the back seat perhaps. Best of luck with this repair.

 

We've had good success with 3M High Bond Rear View Mirror Adhesive ;
https://www.3m.com/3M/en_US/p/d/b40066497/