SD CARD MAP

The map on the SD card changes names based on the model of your Nuvi. The older ones had to have the SD card map named GMAPSUPP or something similar while the newer models use a different name.

Welcome to The Factory.

There are a couple reasons why your North America map can be used by your nuvi 40 but not your nuvi 670:

1) The nuvi 6x0 series is one of the Garmin nuvi series that can not read files larger than 2GB in size. The current North America map file is larger than 2GB and therefore the map will not appear:

http://www.poi-factory.com/node/42561

2) If your SD card with the map that's being used in the nuvi 40 was a map update done by you if your nuvi had lifetime map updates, know that City Navigator map updates can only be used on the device it was made for; i.e., if you updated your nuvi 40 with City Navigator North America with the map being installed to the SD card, the SD card's map can only be used in that particular nuvi 40. The map will remain locked and unusable in any other Garmin GPS.

Since your profile indicates you are in Leinster, I assume that's in Ireland. Therefore you have a Nuvi 40. with European maps ( Probably UK & Ireland). If you have Lifetime Updates on the Nuvi 40 it would be only for UK & Ireland.
Your 670 came with North America & Europe maps loaded but NOT with lifetime Maps, so those will be old maps on that unit.

Knowing that, I assume you bought an SD card with North America maps. An SD card that was purchased for a specific area will be recognized in all models provided the map is in the proper folder on the SD card and proper naming.
You CANNOT copy the map to another SD card since it's locked to the serial number of that SD card.
On your Nuvi 670 it would be in a the Garmin folder on the SD card with the name gmapsupp.img.

I do believe the reason your 670 won't recognize the map is as CraigW mentioned the 600 Nuvi series cannot read a map over 2GB and the Full North America map is over 2 GB.

Kindly advise how the North America map on the SD card was obtained, was it an SD card purchase or a download from Garmin.

Both garmins are USA bought,but only cover 49 states, I got the Canada maps from a download site. The nuvi40 will read the Canada map while the other unit will not.

If by "download site" you mean that you have Garmin maps that you downloaded from the internet and didn't pay for them, then I'm affard we can't help you as it's against forum policy to discuss the use of "privated" maps. On the other hand if you have downloaded non Garmin maps from a site like OpenStreetMaps then that may be legal. Please clarify.

thanks i,ll check the source.

good info here