1) Check Your Battery. If your stud finder worked previously, but no longer seems to work, about 9 times out of 10, the problem is a weak battery. You may swear that the battery is still good, but it's not. ... Compared to garage doors and many other devices, stud finders require a very strong battery.

Why are stud finders so unreliable?

Most magnet-type stud finders don't work effectively since they reply on locating the fasteners (screws) used to secure the drywall. These can be very difficult to locate.

What do you do if your stud finder doesn't work?

To locate the studs in the wall, you can use a stud finder. If your stud finder is not working, check the battery, review the instructional manual, and determine whether it's an edge or center finder. Also, try calibrating the device and check whether your walls are too thick due to lathe or plaster.