Is there a way to get water stains off of wall paper?

If you have wall paper left from this room, I would cut it out and replace it with new paper. Scrub the glue off the wall, let it dry completely. Replace the paper. To remove the paper, start with a paint tray and hot water. Take the roller and roll into the water, and drain excess off. Roll from the bottom up, and remove the paper by scraping from the bottom up with as putty knife.

Insurance claim?

try rubbing with stale bread this is a good wallpaper cleaner. But if the water stain has soaked right through the paper it might be easier to replace if this doesn't work.

http://www.howtocleanstuff.net/how-to-remove-water-stains-from-wallpaper/

Try Mister Clean sponges. Wet and then squeeze out all the water. Good luck.

Personally, I would never use wallpaper around anything that might leak, steam up, or condense - just like a bathroom. I'd use at least a semigloss paint instead because whatever leaked before might leak again. It will make it easier to wipe up the water stains with a warm sponge.

Rather than remove and/or replace all that wallpaper, you could try painting it using a special primer that covers stain. Here in Canada, we have a product called Kilz primer which is supposed to cover most stains. Best wishes.

I don't think you will be able to clean it, but you might be able to cover the stain by getting Stain Cover to spray over it and then you will be able to paint it. That's the only easy and cheap way to fix it. Oh! just thought, could it be covered by a picture or mirror etc......

Your more important problem, imo, is the AC leaking. To install this in the attic, it needs to have a method for draining the water that definitely occur again and again. Whoever installed should have know this and you may be accumulating mold in the attic and in your duct system. The hot attic with moisture is a perfect breeding ground for mold. No matter where you place the AC in the attic, it needs a drain system.