1. Disconnect your Garmin GPS from its external power and completely turn it off. ... 2. Flip the Garmin GPS antenna if your unit has one. ... 3. Press the "Reset" button on the backside of the unit. ... 4. Reconnect your GPS unit to any external power source like the car plug, your PC, or wall charger. Contact Garmin Support via Internet or telephone if the "Reset" button has not fixed the problem.