@batman : Yep, since it's the section I'm working on, I specifically tested all ignition switch wires, the rectifier wires, the turn signal relay wires, etc.
What bugs me is that only the turn signals are not working, the other lights work (stop, license plate, headlight...)
@verslagen1 : previous owner already modified the harness, some parts were covered with electrical tape, some wires were connected together by pressing some metal thingy with a plier (Don't know how it's called), he also added a tachometer soldered on the ignition switch, etc
Edit : btw, the orange and black wires of the rectifier also seemed to have been moved before, which is why even if I removed the wrap I did not have enough wire lenght to relocate it where I wanted to