Originally Posted by
vandalarchitect
It happens to from time to time when I clean my bike. I know some have used a different, stronger magnet on the crank and have had good results so if this is something that regularly happens you might think about it.
RE: the magnet.... I also use one of those powerful little disk magnets (called rare earth magnet in some circles) stuck right onto the inner surface of the pedal spindle and it works great with my Garmin cadence sensor. Will not come of accidently. I found mine in a 6 or 8 pack at the local craft store, but they're usually available at radio shack. Less than a buck a piece, probably closer to $.50.
I don't think that has anything to do with OP's problem - which I agree is that he probably just bumped the sensor and/or needs to re-do the procedure to get it to communicate with the garmin. But the disk magnet is a neat little installation, no zip ties.