How to add new map sections without erasing current maps?

Then when you add the Mexico map it will be added as a supplemental map. If the 2009 map was loaded via mapsource it would be loaded as a supplemental map and when you add a map from Mexico it will write over the 2009 map. You can select 2009 maps in mapsource, then change to Mexico maps and select them and then load all to your gps or sd card... It's kind of like the pois it writes over previously installed files.

I'm not adding maps via update. I have 2009 US/Canada Maps on the Nuvi. I went to add one section of the 2008 Mexico Maps via Mapsource. It erased my 2009 US/Canada Maps and added the one mexico section map. How do I add something specifically as a supplemental map?

Open 2009 North America mapset. Select using map tool any or all maps as desired. Now open the Mesico mapset, select maps desired again using the map tool. Now select send to device with your gps attached to your computer and select your gps or sd card as desired. Click on maps in what to send. Then select send....

BTW If you want to select the entire North America mapset, zoom out to 1500 miles, Left click on your mouse with the pointer positioned to the upper left or right area and drag a square over the entire mapset... That will select all of the maps.

Mapsource only ever adds supplemental maps. If it erased your US maps, then, they too must have been installed as supplemental maps (somehow).

In practice, this is just controlled by the filenames involved.

Supplemental maps live in GMAPSUPP.IMG

Normal/Main/Primary maps live in GMAPPROM.IMG (and/or GMAPPROM1.IMG)

How did your 2009 US maps get on there in the first place? ... via an upgrade from DVD?

I had the 2008 maps on my unit originally. I went to mapsource and tried to upload the 2009 maps and it didnt have enough room, so i uploaded my 2009 maps by deleting the 900mb img file from the garmin disc and then transferred the 2009 maps through mapsource. so do i just not have a primary map on my unit? what is the proper way to add primary maps?

That was the wrong way. You should have run the update program in order to have the program overwrite the preloaded maps and thus create a new PRELOADED MAP FILE in the form of a file named GMAPPROM.IMG.

This would have protected it from being overwritten by new maps sent from MapSource.

What you need to do is to reload the City Navigator North America maps. The preferred way would be to load them by running the update program. However, I'm not sure if that's possible now. Try it.

If it doesn't work, then you will need to create the mapset for just City Navigator North America. Send that to the nuvi. Then rename the GMAPSUPP.IMG file to GMAPPROM.IMG.

Then send the other maps, although I didn't think that there was enough space directly on that unit to load all those maps. You may need to load them to the SD card.

Thank you, I will try that. Didn't even know there was a way to update the maps any other way. I will get out my mapsource DVD and play around. To note, the North America (US/Canada/PR) set is about 1100 MB. The mexico maps are only 137 MB big. My Nuvi 200 has I believe 1.5 GB. I have been able to load the full north america and Mexico maps as a supplemental file and it fits along with about 8 - 10 POI files.