There are a few instances in which it may be necessary to perform a master reset on the Edge. A master reset should be performed if the Edge is:
All settings, workouts and satellite data may be erased when resetting the GPS. Workouts can be backed up in Garmin Connect. Refer to the FAQ article "How can I backup my personal settings and profiles on my Edge 510, 810, Touring or Touring Plus?" to back up personalized settings.
To perform the master reset:
The Edge is now reset if the device finishes powering up and goes to the setup wizard. Try the steps again if the setup wizard does not appear.
Leave the device outside with a clear view of the sky for a minimum of 20 minutes to acquire satellite data.
1A User Data Clear can be performed in order to remove personal settings without removing history.
To perform the User Data Clear:
This will erase personal settings, such as the user profile. However, saved activities will not be removed.
2Not available on Edge Touring
3Not available on Edge Touring Plus
Garmin Connect - http://connect.garmin.com/?s=1