The wiring diagrams are online as part of the factory manual for W126.

startekinfo.com, select workshop resources on the left, page through for chassis 126 manuals.

If that doesn't work, the seats for an 86 126 ought to be similar to a 124. There is a nice copy of the 124 wiring diagram (cleaner than the official MB one) at w124-zone.com You'll have to sign up but it's free.

From what I heard, they had a fire in their archives and the master copies of all the service data for the older models was destroyed. They had to find a paper copy of the books and scan them in.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech