Sat nav problem

Bought identical sat nav ,I supose the older type Infotelematic connect nav, from ebay mainly for the discs for a 2002 doblo,however on fitting ,all the connections are correct, it glimmers for 5seconds then goes out,thats all I can get out of it,is there a fault with it?or just not exchangeable,could some also tell me as well where are the bus cam lines wires,mentioned here,regards ,bucca.