PDF Manuals

Some useful manuals and diagrams in PDF form to download [from Dropbox]:

European BMW E21 Owner's Manual - https://www.dropbox.com/s/xc7l6nfe8v4ke9q/BMWE21EuroOwnersManualComplete.pdf 8.6MB

BMW E21 Workshop / Service Manual - https://www.dropbox.com/s/57ft3vv31fsroyh/BMW_3_75-82_Workshop_Manual_Russian.pdf
[good diagrams, but sadly text is in Russian.]
45.3MB

E21 1981-83 Electrical Wiring Diagrams - https://www.dropbox.com/s/z0gy7fk7hqt1rzs/E21_1981-1983_Wiring_Diagrams.pdf
[some differences between Euro/US and model variants, but a great basic guide.]
4.3MB

E21 All Models/Years Parts Catalogue - https://www.dropbox.com/s/6a2eu8ioz42otdw/E21_Parts_Diagram_Catalogue.pdf
[good exploded parts and assembly diagrams.]
7.4MB

E30 Electrical Troubleshooting Guide + Wiring Diagrams 8.9MB https://www.beemerlab.org/2022/02/e30-316i-318i-electrical.html

RealOEM.com has a wealth of E21 diagrams, direct from BMW workshop documents.