Hello,
Thank you for your kind words.
Again, the rear heater switch indicates it is a Europe spec 75 Series.
It appears your harness has provision for a 4WD switch and a mirror control switch.
Your truck has a differential lockers switch, which suggests your harness has some extra plugs. There should be a 4WD ECU between the pedals and the fuse box.
I may be stating the obvious here. The PO hacked some AC control in the switch panel. Cheaper than getting the whole setup, including the switch, I guess.
By the way, the boxes/tables with lines and circles in the wiring diagram show how the circuit operates under different switch positions, as well as where to check for electrical continuity when troubleshooting.
Juan