Channel Bonding Adhesive
FYI, 3-M Channel Boding Adhesive works just fine. Once I've used this stuff, I have never had to re-glue a window yet.
My wife's old 77 Marquis had those slide-down vent windows. They had to be glued in place. I first tried some other kind of window adhesive and it didn't last for squat. After using the 3-M stuff, I never had another problem with them. Seven years and no problems. The driver's side front window had to be opened every day since the wife had to use a key-card to gain entrance to her workplace parking lot. If you have seen the sequence of the window operation, first the vent window goes down, then the main window goes. That's a lot of window use, in all sorts of weather. No problems with the window once I set them with the Channel Bonding Adhesive.
If you follow the directions correctly, making certain that the glass is clean, with absolutely no residue on it, it works fine. Lacquer thinner is best to use here. I went the extra step and sanded the window surface a bit where the glue was going to be to give it some extra 'bite' surface.
What I'm trying to say is don't be afraid to try regluing your glass. What do you have to lose? Just make sure you use the right stuff!
The 3-M stuff is available at most parts stores that cater to the professionals. Forget Pep Boys, and Auto Zone here. They'll look at you funny then try to sell you normal runny-assed epoxy. The 3-M stuff ain't cheap either. about $12 for the twin tube applicator. You don't need the mixing gun. just squirt out equal parts (use a stick or socket extension that you have marked for a certain depth), mix, and apply. You have about five minutes working time at normal room temperature. Next leave it alone for a couple of hours before attempting to move the window or clean up the excess. Use a razor blade to scrape up the excess.
Mark the location of the channel on the glass with a permanent marker. I normally clean up the channel off the car to remove old stuff from the channel to make room for the new glue. then reinstall the channel. Mix the glue, then fill channel. install glass. Yes, I'm installing the glass when with the regulator and channel in the door. It works best making sure you get the angle right. Hey, you have the door panels off anyway, so it really is easy.