I’m a strong proponent of using a Garmin GSC 10 Speed/Cadence Sensor to eliminate under-measurement when using a Garmin Edge 500 bike computer. When I found the GSC 10 on my Salsa El Mariachi single speed to have stopped recording wheel revolutions I was a bit disappointed. I didn’t really want to spend $40 – $50 on another one, so I phoned Garmin and asked about a replacement.
I found that the reed switch on the extended arm (the part that detects wheel rotation) would only intermittently trigger if a large neodymium magnet was rubbed on it. Tapping on it didn’t free up the apparently sticky reed switch either, so I figured it to be dead.
Garmin has been good to me in the past about warranty issues (namely, replacing an Garmin eTrex Legend whose input stick ceased working) so I decided to give them a call. After talking with the phone support person for a few minutes and explaining the problem he agreed that it seemed defective and offered to send out another. It arrived today, and now my single speed has a working sensor again and should properly measure distance on trails.