Just found this on the Airstream website (http://www.airstream.com/service/manuals/):

Airstream Westfalia Parts Catalog

Here are the diagnostic/testing manuals for the 2006 Sprinter. The US Airstream Westfalias are built on a 2004 chassis, but the differences should be minimal, or none.

There are four parts to the manual:

• 2006 Sprinter Service Manual: Body
• 2006 Sprinter Service Manual: Chassis
• 2006 Sprinter Service Manual: Powertrain
• 2006 Sprinter Service Manual: Transmission

Thanks to Juju for these manuals!

This is the ‘Motorhome Supplement’ that came with the owner’s manual, for the 2005 Airstream Westfalia campervan.

Scanned from the original, into PDF.

Link: Sprinter Westfalia Motorhome Supplement

This is the testing and repair manual, with electrical diagrams, for the Airstream Westfalia.

It’s been converted to PDF for easy printing and portability. 40MB, 1049 pages.

Link: Airstream Sprinter Westfalia Repair, Testing, and Electrical Manual