Cycle analyst speedo

I have a 60v system with 20 Thundersky 60 ah cells,a Perm 132 motor and a cycle analyst to monitor speed amps etc. The speedo function of the analyst uses a magnet and sensor to sense wheel rotation and calculate speed. It was working fine and then all of the sudden it quit. I remember seeing somewhere that a guy hooked his up to his motor but it was not the Perm. The magnet thing seems kind of funky and I was woundering if anyone knows of a better set up.