o.k., battery in engine bay, that is important for us. As a general rule we can say the fusible link is always close to the battery. Looks like it is a 50A fusible link.
Here - that is again a US 525 - they show that that fusible link is 80A http://www.bmwe34.net/E34main/Mainte...sible_link.htm
the failure syndromes they mention there = Failure syndromes: Intermittent simultaneous failure of wipers, sunroof, windows, central locking, radio, No power, like if the battery was dead = that is mainlyl GM related = Zentrale Karrosserie Elektronik.
It may be that your 518 has only one fusible link.

still searching in the net for a matching Stromlaufplan / wiring diagram, the German E34 forum has these https://www.e34.de/tips_tricks/schal...haltplaene.htm

here we come closer, 1994 518i is listed there, wayback machine helps https://web.archive.org/web/20070416...w_e34/E34.html
check it, not all pages work there.
German language Werkstandhandbuch Schaltplaene E34, also includes 518 https://www.ebay.at/sch/sis.html?_it...k&_mPrRngCbx=1
maybe the cheap CD will do instead of the books. Or here in Augsburg per book 50 EUR https://www.ebay-kleinanzeigen.de/s-...37140-241-7525
Original BMW Ordner
Modelljahr 1988 525i,530i,535i, 1988 520i,524td, 1989 525i,530i,535i,M5, 1989 518,520i,524td, 1991 518,520i,524td, 1991 525i,535i,M5 2 Ordner, 1992 518i,520i,525tds 2 Ordner, 1992 525i,535i,M5 2 Ordner, 1993 518i,520i,525tds 2 Ordner, 1993 525i,M5 2 Ordner, 1994 518i,520i,525td/tds 2 Ordner, 1994 525i,M5 2 Ordner, 1995 518i,520i,525td/tds 2 Ordner, 1995 525i,M5 2 Ordner, 1996 525i,M5 2 Ordner, Preis pro Ordner, Versand gegen Portogebühr