: You can find a comprehensive set of Audi A4 (B7/8E) Workshop Manuals and Wiring Diagrams available for free download or online viewing.

: Frequently hosts user-uploaded manuals. For example, a 5-page Radio Wiring Diagram for the Audi A4 is available for viewing and download.

: Platforms like vwts.ru provide downloadable PDFs of original current flow diagrams.

: The most accurate source is Audi erWin , where you can access official factory manuals, including detailed electrical schematics, via a time-based subscription.