Look for the red wires. The E39 has multiple power distribution points:
The BMW E39 is a masterpiece of engineering, but its electrical system is not forgiving. By obtaining a professional-quality and learning how to trace wires using the color codes and connector indexes above, you can save thousands of dollars in diagnostic fees. Schema Electrique Bmw E39
: Une application mobile pratique pour consulter les schémas directement sous le capot. WDS BMWland Look for the red wires
The E39 is extremely sensitive to voltage. A failing battery or alternator diode will trigger "Trans Failsafe Prog" and illuminate the ABS light. : Une application mobile pratique pour consulter les
Fan runs on high speed even with key off. The Fix: The schematics show the IHKA (Climate control) panel sends a variable ground signal to the FSR (located near the gas pedal). Cut the old one out, solder a new one in. Pro tip: Look for wire color "RT/BR" (Red/Brown) for power and "BR" (Brown) for ground to test.
Keep your multimeter handy, keep your wiring diagram laminated, and your E39 will run for another 200,000 miles.