How do I fix a bathroom light Fixture that is falling off the wall?
You'll know more when you undo the screws or thumbscrews holding the fixture onto the gangbox.


If the gangbox itself is secure, then you have some mechanical problem with the fixture or its screws or the threads on the box.
If the gangbox is insecure and is being pulled out of the wall,

You can use Madison Straps (less than a dollar) to keep the box in the wall: the long part of the strap slips in next to the box and behind the wall (slide up the long end first, then slide the short down so both top and bottom are providing support), then the short straps bend over right into the box to keep the box from coming of the hole.
You can pull out the loose box and replace it with an old-work box, which has surface-flush flanges to keep the box from falling in, and little clamps that flip up when you tighten their screws, pulling the box tight to the wall.

If the gangbox is insecure because it's falling into the wall, perhaps you need to firm up the crumbling hole you're trying to secure something into: new drywall from stud to stud, or some other mechanical reinforcement of the wall itself.  If you're opening up the wall, use a new work gangbox that can be fastened to a stud instead of the relatively flimsy drywall/plaster.


Does it go without saying here that you should only do things you understand, and that the circuit's power should be off while you're doing this?