I'm taking this question from when I wired the OD in my 140. At that time, I discovered there were configurations where the 12V source was directly connected to the solenoid, but through the OD switch and the 4th gear lockout switch. Thus, if either switch was open, the solenoid wouldn't actuate. Downside was that full current would run through the switch. However, this must have been Volvo sanctioned at one point, because I remember seeing 1800 diagrams showing such a configuration.

Fast forward to wiring the OD for my 240. I'm going to be using the old style slide switch on the shifter, which means I think I could wire this the same way with 12 V going to the switch, then to the 4th gear switch, then to the solenoid. This would greatly simplify the current wiring with that relay that never works anyway. Is there a reason I can't do this on the later cars? I remember deciding the solenoid current on the 140 was small enough that it was safe. Is that true here?