for download here http://www.jtresto.com/e21info.htm
includes:

Bosch Warm Up Regulator Assembly and Disassembly - PDF File
320i Electrical Trouble Shooting Introduction - PDF File
ETM - 1977 Wiring Schematic - PDF File
ETM - 1978 Wiring Schematic - PDF File
ETM - 1979 Wiring Schematic - PDF File
ETM - 1980 Wiring Schematic - PDF File
ETM - 1981-1983 Wiring Schematic - PDF File

workshop manual here https://www.bmwtechinfo.com/repair/main/

Includes:
Repair Information
Nominal Values, Specifications and Tightening Torques