As I know it is for electric windows, electric dooor locks and alarm. Might also control interior lights.
On a Passat, the battery is located under the hood. It is under the cowl panel and requires the removal of the battery cover to see it.
I was able to stop power to my malfunctioning windows by removing the "metal fuse" as detailed here. http://www.passatworld.com/forums/showthread.php?p=2501518
The 2005 Volkswagen Passat is a gas-powered vehicle.
The 2003 Volkswagen Passat is a gas-powered vehicle.
The 2007 Volkswagen Passat is a gas-powered vehicle.
The 2001 Volkswagen Passat is a gas-powered vehicle.
The 2002 Volkswagen Passat is a gas-powered vehicle.
The 2010 Volkswagen Passat is a gas-powered vehicle.
The 2004 Volkswagen Passat is a gas-powered vehicle.
The 2013 Volkswagen Passat is a gas-powered vehicle.
The 2012 Volkswagen Passat is a gas-powered vehicle.