Garmin MapInstall 4GB Limit

I have recently had problems when updating the Lifetime maps from Garmin using Garmin Express, the download fails with an 'Error' message, there are 3 options when performing a map download using Express, they are 'To GPS unit only', 'To computer only' and 'To both GPS unit and computer', I used to select this last one so that I could use the map with Garmin Basecamp even when the GPS wasn't connected to the computer, however If you are getting download failures I would select 'To computer only', This will allow you to see the new map in Garmin Basecamp and then use Basecamp to send the map (or part of it) to your GPS.

In my case the 'Error' was due to Express being unable to find suitable free memory on the GPS unit (a Nuvi56 satnav) with 8GB internal memory and an 8GB microSD card, it had the previously installed City Navigator Europe map=2.4GB, and 2 third party maps, (OSM=700MB and Toasty Talker=2.3GB), all of which were on the internal 8GB leaving only a few hundred MB free, the problem was that although there was an almost empty 8GB microSD with only 140MB world maps on it, the new map which was 4.8GB was not sent due to Garmin MapInstall only 'seeing' the microSD as 4GB not 8GB

I would advise that any third party maps be only sent to the microSD so that the original map can reside on the internal memory and there is room to replace it with any updates, MapInstall won't allow the deletion of the original map and it is not shown as present although you can see from the amount of 'Free' space on the internal storage that something is taking up space, With all maps removed from the internal memory my 8GB Nuvi shows about 6GB free


MAPINSTALL 4GB LIMIT
There is a trick to get around this limit, if the a file:- [Internal_Memory]/Garmin/GarminDevice.xml is copied to the same folder on the microSD then Mapinstall will see all of the 8GB capacity on this memory card and will allow a 4.8GB map to be sent to it, NOTE:- due to FAT32 restrictions Mapinstall will split the map into 2 or more sections so that no single file exceeds 4GB, This fix does however cause another problem as previously the internal memory is named nüvi 56 and the microSD is allocated a drive letter and called 'Memory', If GarminDevice.xml is copied to the micoSD this device will have the same name in the Mapinstall selection screen, it is possible to get around this by editing the GarminDevice.xml (after making a copy of the original) and renaming the device so <Description>nüvi 56</Description> becomes <Description>nüvi 56-SD</Description>

NOTES

1. you should not delete or edit the original GarminDevice.xml on the internal memory, if you encounter any problems, delete the copy of GarminDevice.xml on the microSD to return the unit to normal
2. If your microSD already has a /Garmin/GarminDevice.xml file, do-not over write it with the file from the internal file system
3. The FAT32 file system used by Garmin will allow a maximum single file size of 4GB, multiple files up to this limit are allowed in FAT32, MapInstall seeing larger microSD as 4GB is not related to this FAT32 limit