I have a nice Sigma computer that I've used for about 10,000km. I just took it out recently and the damn thing isn't working. The reason is that the magnet part (the bit that clips on to the spoke) is no longer magnetized. (If I swipe a magnet by the sensor, the computer picks it up, so it's just a matter of fixing this little piece.)
How can I re-magnetize that little piece of plastic-encased metal that clips onto the spokes??