I bought a compass today. I tested it at the store, multiple times, spinning all which ways. It would always immediately spin itself around to accurately point north.. It is one of those ball compasses like what's on the back of a survival knife. As soon as I got home it stopped pointing itself north when I would turn it. if I shake it it will sometimes point north but just as often it will wind up pointing south, west or east. I tried it outside on the porch as well. It still doesn't know the difference between north south west or east. When I run a magnet around it from 3 - 4 inches away from it, it spins and follows the magnet. For that reason I assume the compass works, but then why won't it point north?