A magnetic compass can lose it's magnetic ability to track to the earth's magnetic North. Sometimes this can be caused by poor manufacturing quality or perhaps the comapss was left near a stero speaker which can ruin the magnetic abilities of the compass needle/compass card. Usually a compass will start to lose it's "North seeking" ability simply due to age.
In the early years of sea navigating ships, one of the most important items was the ship's compass. A ship's compass was often stored within and attached to a box by means of a gimbal so that the compass would always be level so as to allow the compass needle to easily settle to magnetic North. More modern gimabls were called "Binnacles".
But little do most people know that there was one other item just as important and perhaps more important than the ship's compass. It was a "Lodestone", (pronounced "Loadstone"). It was usually a piece of strong magnetite and used to remagnetize the ships compass needle because early compasses would lose the magnetic North tracking ability or magnetism because older ship compass needles never stayed permanentaly magnetized. Additionally, if the ship's compass were lost, stolen, or damaged, a simple piece of small iron bar could be magnetized and used as a make-shift compass.
A modern substitute for a lode stone can be a neodymium magnet. The South end of the magnet can be used to remagnetize any compass needle or compass card so that it tracks and settles to magnetic North accurately and more quickly.
To find the South end of a rare earth/neodymium magnet, hold one end of the magnet and inch or so from the side edge of the compass body. If the North end of the compass needle is attracted to that end, you've found the "South" end of the magnet. If the South end of the needle is attracted to the magnet, you've found the "North" end of the magnet. Remember, "opposites attract" when it comes to things magnetic.
Mark the South end of the magnet "S" so you know which end is South.
With masking tape, tape the South end of the magnet onto the side edge of the compass body and leave it for an hour to a day or so. In honsety, even a few short minutes will remagnetize your compass needle, but some prefer to leave the magnet tapped to the compass for a few days. If you make a mistake and tape the North end of the magnet to the compass, your "South" end of the compass needle will now point North. No need for worry. Simply reverse and tape the South end of the magnet to the compass and it will chnage the magnetic polarity back to where it needs to be.