2000 E350, only defrost vents work

Had the exact issue, no a/c going to the vents in the dash. Traced the black vacuum line from the top of the engine across the top vent panel to under the battery tray into the cab of the truck. Seems a mouse ate the line in 3 places. Went to Auto Zone bought a piece of line and a connector pack, $8.00. Removed the air cleaner unit, pulled out the battery and battery tray. Removed the right kick panel inside the cab and found the line. Pushed a screw driver, long one through the firewall where that line went through and taped the new line to the screw driver to pull the new line into the cab. Used the new connector to connect the line in the cab. Ran the line back under the battery tray and up to the area where the mouse ate the line and used the new connector to connect them together. Fixed, and about 45 minutes. Hope your is as easy to fix.