My Garmin SPIII is powered from an extension lead that is piggy backed onto the accessory socket on the left had side. Every now and then it loses external power for no apparent reason and goes onto battery power. I have to switch off the SPIII and the engine and restart, sometimes it will do this 3/4 times in quick succession before settling down and the external power stays constant. Any idea what is causing this.....never had this problem with my 1150....mutter mutter.
