How to Reset the Garmin Forerunner 305by Nick Peers
Perform a soft reset on your Garmin Forerunner 305 if you can't turn it on or if it doesn't charge properly. A soft reset does not erase any data from your device. If your GPS unit can't connect to satellites, can't pair with other devices or isn't functioning properly, perform a hard reset to fix the problem. A hard reset erases all the data on your Garmin unit, including settings, workouts and courses.
Perform a Soft Reset
Connect the Garmin Forerunner 305 to your computer using the cable that shipped with the device. Hold the "Mode" and "Lap/Reset" buttons for 10 seconds and then turn on the GPS unit. Download and install the Garmin WebUpdater application (link in Resources) and follow the instructions to update the firmware of the Forerunner. Disconnect the device from your computer after updating the firmware.
Perform a Hard Reset
Turn off the Forerunner 305 unit, if it's not already turned off, and then hold the "Mode" and "Power" buttons until the "Do you really want to erase all user data" message appears. Select "Yes" only if you are certain you want to perform the hard reset. All settings and user data are erased from the device during the reset. The device is reset to factory defaults, so you must leave it outside for at least 15 minutes to reacquire satellite data.