Recently looking at relay board wiring. I think I have it all figured out except for terminal #3 on the engine connector. #3 appears to get switched ignition power via the 25A relay board mounted fuse from terminal #11 on the relay board harness connector from the cabin .

Where does it distribute this power to?? Neither of my two wiring diagrams clearly show that power going anywhere

I'll get back to you with an answer later today

Thanks Perry

A quick check shows:

1 - B on CD box
2 - Points and C on CD box
3 - not connected
4 - Accelerator position switch (US emissions)
5 - not connected
6 - Thermal Time switch
7 - Thermal Time switch
8 - A on CD box
9 - Oil Pressure
10 - Cold Start
11 - Oil Temperature
12 - Back-up switch
13 - not connected
14 - Back-up switch

I will look at the other schematics and see if they differ

I still haven't had a chance to check, but IIRC #3 is what I call the "914-6 green mystery" wire in the chassis harness that goes up to the gauge cluster.

You can use this to add an oil press gauge without having to poke an extra wire in the cabin. In the engine compartment you can get an awesome reproduction engine harness from me, or the easiest option to pirate the cold start or termo time switch wires and move it to the correct terminal in the 14 pin plug.

Hijack alert**

That is good news, I wasn't looking forward to running an oil pressure wire up to the front.

Hopefully this will be clear in my harness you are making for me.

Perry. It is my understanding that the green mystery wire was put there for use in the sporto equipped cars for a trans temp signal to a light in the combo gage. I do not have my diagrams in front of me but I believe it is #13 on the engine connector and maybe #3 on the main connector. I used that wire for an oil pressure signal to my combo gage.

I am currently installing a rear mounted engine oil cooler with a thermostatically controlled fan (I know, not as good as a front mount). I was looking for a wire that I could use to light a light on the instrument panel to tell me when the fan is running. I found the normally unused rear window heat switch YR wire from #5 on the main connector. I will jumper my "indicator" wire into the correct pin at the window heat relay socket and use the YR wire to go to the panel.

In studying the diagram for the relay board looking for an unused wire, I was able to understand all the wires except #3 on the engine connector. It clearly gets 12v via the one 25A fuse but I can not see what it feeds. Just curious.

By the way, the YR and the G wires are the only two "unused" wires I could find in the stock six harness going from engine compartment to dash. Kinda wish there were more but at least we have these two!

Lawrence, I think they are talking real 6 harness, not a 914/6 conversion car, you may not have this wire.
Also in a /4 harness that pin could be totally something else so take care.

In a conversion car I utilize the heater blower switch wire for the oil pressure gauge. It's easier without the engine relay panel, but you can make it work either way.

Yes did this along with one of Perry's excellent looms ,its pretty easy and works but as suggested it might only work if you have the 4 cyl loom.
I also powered my fuel pump off the rear window heater circuit as my original FI pump circuit was dead.

Did a little browsing on the Art Zapf 914-6 wiring diagram. Terminal #3 on the engine harness (as pointed out by GMS) is not used.

I haven't confirmed this by checking a 6 relay board but it looks like #3 goes to what Zapf calls the "primary control unit" which looks to the RPM transducer for the idle position circuit, which I think may have been optional for a MFI engine. I have no proof of that however. I'd love to seen how the few 916's with MFI were wired.

The "914-6 green mystery wire" goes through the relay board to terminal #13, which is not used in the stock 6 engine harness.

I have an NOS 914-6 Sporto engine harness. I need to dig it out of the moth balls and do a little recon on it.

That would be interesting to confirm the sporto wire. I have my six board out. I will trace the wires and try confirm all of the "primary control wires" and trace the other relay related wires.

Won't happen until later this week

Great info.
Oil press. gauge without additional chassis length wire.