Would it be possible to hook up one of the express-down modules to the passengers window as well?

If you have a spare module and plug I think so. This is one of those things on my list to do. It may have to be mounted in the drivers' door though.

Well I've got an 89 parts car that has the module with a busted button. How does it hook up to the switch in the door?

M'kay, Got my book out, Page 8A-120-0.

You need to tap the Pink wire for constant power.
Tap the Dark Blue for "Up Button" sensing.
Cut the Brown wire, Patch it to the Brown wire in the Express Down Module. Then patch the Brown/White wire into the Brown that you cut, going to the window motor for Down control.
And of course put the module in the passenger door.

Now, Get someone to change the wire colors over to your year and you're set. Meanwhile I'm going to go patch mine in right quick, That'* just too easy to pass up.

Actually I want to put it in the drivers door as well. That way I can put them both down at the same time from the drivers side. Its just looks cool to put your windows down hands-free

Sweet. Installed and working. It has to be put in the passenger door to work, But it'* sweet as hell. Install took what? 30min? I soldered it in and everything. Had to look my electrical tape too... I have the module zip tied to the door about where it is on the other side. Works perfectly and looks cool as hell.

Why can't it be put into the drivers door as well?

If you put it in the drivers' door the passenger can't use the express down module.

[That'* what I am looking for. I just want the express down for the drivers side controls only. The passenger side i still want to be manual.

Okey, Now we either need to get someone with your years' FSM, Or you can jump in your door with a multimeter.