Nice work, Captain Obvious. Thanks for your persistence in moving this forward. A few questions and comments specific to the Combination Switch:

1. I see the Horn Relay, but I don't see the Horn Switch (talking about the 'switch' that operates when the driver pushes on the horn pad)
   

2. Letters appear in some of the rows in Column 2 of the 'grid' for the Combination Switch (the letters are: A, B, D, E, F, M and P). Can you refresh my memory as to what they stand for?
   

3. As currently depicted, the Wipers show only 'OFF' and 'ON' modes, with the logic within the 'ON' mode apparently trying to do double-duty for both 'HI' and 'LO'. I think that the switch's operation might be more clear if 'ON' is replaced with discrete 'HI' and 'LO' modes. See attached schematic, per my original post in this thread back in July 2024.
   

4. As I also pointed out back in 2024, it's worth keeping in mind that the colours of the wires coming off the Combo Switch don't always match the colours of the wires to which they connect on the Vehicle harness. See below (bold-face letters are Vehicle-side, regular-face letters are Switch-side)...
   
   

Edited June 8Jun 8 by Namerow

Namerow, thanks for the input, and also thanks for the work you had done previously with the wiring. Your previous work helped me with the diagram that I've been working on. So for the comments above...

First, the horn. I understand the desire to have an actual switch depicted on the diagram. And in one of my earlier revisions, I actually did have one in there. But then I took it back out because I decided that I wanted to conform more closely to the original scheme depicted in the other areas of the combo switch. By that, I mean... There aren't any actual switches shown for any of the combo switch functions. Not for the headlights, the wipers... No switches for anything. Instead, "connection" is indicated by the existence of the dot. I though it would be closer to Datsun's original scheme to have a dot connection to ground when the horn is pushed.

Next, the wipers. I haven't dug into that system at all, and I'm kinda hoping that I never have to. I turned mine on and the arms move, and that's hopefully all I need to know. So, with that said... Are you confident in the switch connections you have laid out? If you are sure, I'll change the diagram to what you indicate.

As for the letters in the second column, I'm in the same boat as you... I think I knew at one point, but don't remember. I'll look into it.

And lastly, you are correct about the change of wire colors on the combo switch side of the connectors. Problem is that situation exists all over the car. They got better with that in the diagrams for the later years, but for the early cars, the colors on the diagrams are the "colors of the harness". I'm sorry, but I'm in no position to add all the connectors for all the devices that plug into connectors and indicate the wire colors on both sides of those connectors. Haha!!!

Thanks for the help!

Defroster switch... When did they change from the black unlit design to the yellow backlit version?

Here's a hoovered pic of the unlit black:

And here's the yellow backlit version:

The wiring diagram I've been working on shows the simpler black unlit version. When did they change to the yellow backlighted version?

My 12/70 is black. And my 6/71 is orange/yellow. Still a wide range there.

Edited Tuesday at 01:29 PM1 day by inline6

57 minutes ago, inline6 said:

My 12/70 is black. And my 6/71 is orange/yellow. Still a wide range there.

Interesting, my 12/70 car has the yellow switch. My S/N is HLS30-17486, I'm guessing your 12/70 car has an earlier S/N than mine.

My VIN is HLS3016530. I will double check my memory. It has been a long time since I put eyes on that switch.

Edited Tuesday at 02:32 PM1 day by inline6

14 hours ago, w3wilkes said:

Interesting, my 12/70 car has the yellow switch. My S/N is HLS30-17486, I'm guessing your 12/70 car has an earlier S/N than mine.

My 12/70 #17770 has the black unlit switch.

Haha!! Unfortunately, it's not yet clear:

inline6 - 16530 has the yellow
Johnz1971 - 17770 has the black
w3wilkes - 17486 has the yellow

inline6, when you get a chance, can you double check what you have on your 16530 car?