please follow these instruction and this should help if not let me know and i willcontinue to get you more information for you
the screen of the Garmin StreetPilot C340. If the touch screen does not
seem to respond when you hit it with your finger or a stylus, you may
need to calibrate it. To do this, turn the unit off and then hold down
the "Power" key for approximately one minute. You will see a
calibration screen come up that will recalibrate the GPS unit.
the Garmin StreetPilot C340. If your GPS unit is not responding or is
stuck on a particular screen, it may need to be reset in order to
operate. To reset, remove the face plate of the unit by gently prying
it off. Locate the "Reset" button under the face plate and press down
in order to restart the device.
the fuse of the Garmin StreetPilot C340. If the fuse blows on the GPS,
you will need to make a replacement using an ACG/3AG 2 amp fuse.
Unscrew the adapter cord at the end and remove the fuse found there.
Put in the new fuse to see if this returns function to the unit.
the software for your Garmin StreetPilot C340. If the GPS is not
providing you with correct directional information, you may need to
update the software or download new maps onto the device. Connect the
Garmin StreetPilot C340 with the USB cord to your PC and log on the Garmin website for available updates.