Every couple of years I have to re-attach the rear view mirror to the windshield. I use the glue in the auto parts stores and follow the instructions to the letter. I also park in the sun. Is there a better adhesive?

 

Both surfaces Must be Squeaky clean & Kept clean of the old adhesive & any dash or upholstery plasticizer vapor deposits on the windshield. Those old adhesive & vapor deposits are very difficult to remove, so we need a really good / aggressive cleaner-upper on the glass & metal surfaces & while cleaning or working with them after cleaning, we Must Not touch either surfaces with bare hands, or the old cleaning cloth, or dirty gloves.

SO, wear gloves & be really persnickety about cleaning & handling the parts & adhesive. The cleaning cloth & solvent, or cleaner upper like Bon-Ami, Must Not leave any deposits on the metal, or glass bonding area. So be really persnickety about what you use & how you use them to clean the metal & glass bonding areas & how you handle the cleaned metal part after cleaning. To get a lasting bond it really is important to be that attentive to the Cleaning & Handling Details. Use a fresh, good quality bonding agent from a known good vendor, like Permatex / Loctite.
A bunch of bonding surface prep detail thoughts for consideration, let us know how it goes.

 

I'll get back to you in a year or two, if I'm still alive, and let you know.

 

Before removing the old adhesive on the inside of the winshield, On the Outside surface of the windshield I outline the old glue line residue with a dark ink magic marker, so to look through the windshield from the Inside & visually realign the metal hanging bracket to be bonded.

Remove the glass old bonding residue with a new razor blade & non residual solvent. Apply the solvent to the wiping cloth or towel, Don't spray solvents on the windshield, as they can contact plastic trim or the dash & cause stress cracks or paint problems.

I use 400 grit carbide wet sanding paper on a Flat surface, to Final clean the metal mirror hanger of All old bonding agent & any other contaminates its picked up, so to get down to Bare virgin metal.
Don't use the Wife's perfumed acetone finger nail polish remover, as the perfume oils that make it smell good will contaminate the bonding surface.
We can do a final cleaning with a non residual solvent like say CRC MAF cleaner, onto a plain white paper towel, no ink patterns on the towel that could come off with the solvent & contaminate the surface.
The last cleaning of the surfaces could be a quick spritz of the plastic safe MAF cleaner, then do a water break test to make sure all is staying clean, then let the surface completely dry, then bond, as you know the spray isn't contaminating, or picking up something from the surfaces & depositing them onto the bonding area.
I know it sounds like excessive detail, but if we want a Lasting bond, Both bonding surfaces Must be squeaky clean & Kept that way until the bond is made & the cure is complete, without the part moving.

After cleaning, If the glass & metal part bonding surfaces won't pass the "water break test", they're Not clean, no matter how good they look visually.
To pass the water break test, the bonding surfaces Must wet evenly with a film of water. If the water film beads up, or breaks & runs off, the surface is still contaminated. Once the surface will hold a film of water, they're clean & its bonding time.

I tape the metal hanger to firmly hold it in place until the Full curing time has passed, before rehanging the rear view mirror. More thoughts for consideration.

 

Thanks pawpaw I'll use the information you provided. Are you the gentleman I sent a flasher to several years ago? I remember the name.

 

I don't remember needing, or getting a flasher years ago, must have been another lucky member!!!!

Well I just finally remembered the chemical the plant used to squeaky clean glass, it was ammonium bi-fluoride. I was told decades ago that it would sorta etch the glass on a microscopic level, to get to a virgin surface & to effectively Increase surface area, so the adhesive would have more virgin surface area to bond to, that was squeaky clean, thus we have a stronger bond. So if you can come by some of that, use it carefully with gloves & safety glasses, to clean & sorta microscopically etch the glass, hopefully for a stronger bond.
As I recall I used it to clean the windshield glass when I remounted my 94 Taurus rear view mirror mount about 15 years ago.