If you have a Garmin GPSMap196 please read this.
Current firmware release for the 196 is 4.20, released in March 2006. However there is a problem with it that can cause the unit to switch off at random. What follows is ONLY relevant if you have 4.20 firmware.
How do you know if you have 4.20?
To view the software version, complete the following steps:
1.Press the Menu key twice to access the Main Menu.
2.Select the Setup tab, and press Menu.
3.Select the System Information option and press Enter.
4.The software version will be displayed on screen.
Garmin UK have apparantly been telling Garmin US for a couple of months about this problem but the US are only now starting to take notice and 4.20 is still on offer as a download. The solution is to roll back to 4.10 but 4.10 is not available from the Garmin website and while Garmin UK have it, their procedures prevent them from distributing it. However Garmin UK have pointed me at
this page from which you can download 4.1.
The behaviour seems to be random and is probably affected by hardware differences due to production changes. For my trip to the US I swapped my 196 with a friend's because his has the US Basemap. Being a conscientous chap I checked for updates and updated the firmware in both. Got back for the weekend and flew to Leicester on Sunday with the route already uploaded into Robin's unit. As soon as I started the unit it shut down, tried it several times with the same result. Mine was in the a/c so I fired that up, set up the route and set off. Flew to Monocock's strip at Hungerford, all OK, continued to Leics, still all OK until field in sight when it shut down and did it again when I restarted it. Departed for the return journey and it still wouldn't stay on. Eventually got it to stay on until I got to Didcot when it started shutting down again.
This is an entirely different problem to the other shutdown issue which is caused by the batteries vibrating on their contacts. That one is cured by fitting some foam inside the battery door to hold them firmly in place.
Hope this helps if you get the problem.
Mike