1973 240z Custom Wiring From Scratch

[Matthew Abate]

I've started to redraw my wiring diagram. To give you an idea of how I am changing it from what we have on the site now, here's the fuse box from the original followed by the one I redrew. I wish I could say this will be useful for everyone, but I will be deleting and adding a bunch of components, so it's utility for other people will be limited.

Diagram:

Sample:

Edited September 9, 2022 by Matthew Abate

[Matthew Abate]

Okay, I'm getting close to being done with this diagram, and I have found a number of errors in my tables that I will fix once I have this all sorted out, but I could use some help on the current blocker that I have not been able to figure out.

I am cleaning up the part of the diagram that shows how the Combination and Turn Signal Switches connect to the harnesses in the dash, and I have a few wires I cannot account for. I want to thoroughly understand this because I want to swap this TS switch out for one from a 260Z that I bought from @jfa.series1 for reasons I won't get into here.

Here are the connectors coming off the switches (sorry about the shadow):

• 1 x 9-pin (9 wires)
• 1 x 6-pin (5 wires)
• 1 x 3-pin (3 wires)
• 1 x Large female spade (heavy gauge black wire)
• 1 x Medium female spade (heavy gauge black wire)
• 1 x Small female spade (thin gauge green wire)
• 1 x Male bullet (medium gauge black wire)
• 1 x Male bullet (thin gauge black wire)
• 1 x Male bullet (medium gauge white wire w/ red stripe)
• 1 x Female bullet (medium gauge red wire)

 

Here's the diagram I am working on showing the harness and switches connectors:

 

You can see all the things I am trying to untangle highlighted on the diagram in red:

• Is the Green/Black wire coming from #18 on the turn signal actually the Green wire with the small spade connector on my turn signal switch and goes to the horn relay?
• Do both Red/White wires on the Light & Horn Switch connector go to #15, or does the second, unaccounted for wire go to #17 and just isn't represented in the diagram? These are identical between the 1973 and 1974 switches, although the 1974 has a Green/Black wire coming from #16 rather than a Red/Black wire.
• Are the two black wires with the bullet connectors actually the black wires in the diagram that connect #s 3, 8, 17, and 18? If so, what do they connect to, given they are both male?I have two black wires I can't account for on the harness (one female bullet connector and one female spade connector). I had incorrectly labeled these as for the Door Switch.
• I am pretty sure the second black wire with the spade connector that I have labeled as "Combination Switch XYZ" is actually a duplicate of the one labeled "Turn Signal Switch A" with the white wire and connects #14 to the turn signal flasher.
• The Green/White and Green/Blue wires (#1 & #2) on the Combination Switch connectors are reversed from where they are on the harness connector.
• There is a Yellow/Blue wire on the Combination Switch connector that isn't in the wiring diagram. It comes out of the back of the white box on the switch opposite the Yellow/Black wire, which is also not in the diagram. The wire on the harness in the corresponding position to the Y/L one is Blue/White and goes to the intermittent relay, and the wire on the harness in the corresponding position to the Y/B one is also Y/B and goes to a Blue wire on the engine harness running to the wiper motor.
• I'm pretty sure the rest of the stuff I have captured in the diagram is correct.

 

If anyone has any insights into what's going on here, I would love to hear them! @SteveJ @Zed Head @siteunseen

Edited January 20, 2023 by Matthew Abate

[SteveJ]

 

21 hours ago, Matthew Abate said:

You can see all the things I am trying to untangle highlighted on the diagram in red:

• Is the Green/Black wire coming from #18 on the turn signal actually the Green wire with the small spade connector on my turn signal switch and goes to the horn relay?
• Do both Red/White wires on the Light & Horn Switch connector go to #15, or does the second, unaccounted for wire go to #17 and just isn't represented in the diagram? These are identical between the 1973 and 1974 switches, although the 1974 has a Green/Black wire coming from #16 rather than a Red/Black wire.
• Are the two black wires with the bullet connectors actually the black wires in the diagram that connect #s 3, 8, 17, and 18? If so, what do they connect to, given they are both male? UPDATE: I had three black wires with female bullet connectors labeled as for the Door switch, which is obviously not right. Two of these probably connect to these, so it is a matter of figuring out which ones.
• I am pretty sure the second black wire with the spade connector that I have labeled as "Combination Switch XYZ" is actually a duplicate of the one labeled "Turn Signal Switch A" with the white wire and connects #14 to the turn signal flasher.
• The Green/White and Green/Blue wires (#1 & #2) on the Combination Switch connectors are reversed from where they are on the harness connector.
• There is a Yellow/Blue wire on the Combination Switch connector that isn't in the wiring diagram. It comes out of the back of the white box on the switch opposite the Yellow/Black wire, which is also not in the diagram. The wire on the harness in the corresponding position to the Y/L one is Blue/White and goes to the intermittent relay, and the wire on the harness in the corresponding position to the Y/B one is also Y/B and goes to a Blue wire on the engine harness running to the wiper motor.
• I'm pretty sure the rest of the stuff I have captured in the diagram is correct.

 

If anyone has any insights into what's going on here, I would love to hear them! @SteveJ @Zed Head @siteunseen

The turn signal switch changed between 73 and 74 when Nissan switched to separate bulbs for the brake lights and turn signals. 

1. The GB on #18 and the RB should go like this: 
2. See the diagram above. The RB and RW wires have to meet up with each other on the 3 pin connector. The third wire is for the horn.
3. Wires from 3, 17, and 18 are all grounded. I don't have a photo available to show this. (That also goes to question 2.) It should be a single black wire from the turn signal switch to the headlight switch side.
4. The white wire going to pin #14 on the switch is the power for the turn signals downstream from the turn signal flasher.
5. Yes, the wires are reversed between the wiring harness and the switch.
6. The yellow/blue wire from the 74 wiper controls goes to a yellow/blue in the 74 dash harness and over to the intermittent relay.

 

[Matthew Abate]

Thanks @SteveJ, That clarified some of it for me. The TS Switch that came with the car has two R/W wires instead of one and a GB wire. It's got the RB going to the GB, which threw me off. I'm wondering if it is from an earlier car or something.

Thanks for confirming questions 4 & 5. I guess I will just leave these as is.

The the '73 wiper controls, I have the Yellow / Blue wire switching to a Blue / White wire at the connector which goes to a splice and branches to the intermittent relay and the wiper motor, so I guess it's the same as the '74 routing you described. I guess they just don't represent that wire on the diagram at the wiper switch. You can see where it goes into the switch and them comes out again as a Yellow / Black wire on the oposite side in the photos below.

 

 

As for the rest of it, these are the plugs I still need to figure out:

…on the 1973 Switches

…on the Dash Harnesses

 

• The Female Spade on Dash Harness 2 goes to a yellow splice that also has a black wire with a female bullet on it. I am pretty sure that is for the step light harness, because they're both spliced to a black wire that goes to the body harness and I think around to the other door switch.
  • I am confused by this because the door switch is supposed to be two spade connectors (F&M), not one and a bullet. It's possible I have my wires for the steering lock mislabeled.
• The Female Bullet on Dash Harness 2 comes from the Steering Lock Switch.
• The Female Bullet on Dash Harness 1 comes from the Buzzer.

Once I resolve these plugs I can fix the errors in my tables from before and wrap up this wiring diagram. After that I will make another diagram that has the modifications in it.

Edited January 20, 2023 by Matthew Abate

[SteveJ]

So in examining the 73 & 74 switch diagrams, the blue/yellow goes to switch position 3 on both. I'll look on the 73 dash harness to see where it goes at the intermittent relay, but I may need to be reminded. 

[Matthew Abate]

13 minutes ago, SteveJ said:

So in examining the 73 & 74 switch diagrams, the blue/yellow goes to switch position 3 on both. I'll look on the 73 dash harness to see where it goes at the intermittent relay, but I may need to be reminded. 

I think it's okay. The wires in my harness might be the wrong colors but they are going to the right places.

Something else that is confusing me is the door switches. I looked at the replacements available at various stores and I am seeing three different configurations:

• one female spade connector
• one male bullet connector
• two female spade connectors

[Matthew Abate]

Here's an updated diagram taking into account @SteveJ's comments:

Edited January 20, 2023 by Matthew Abate

[Matthew Abate]

SOLVED!

The second black wire with a female spade connector is not, in fact a spade connector, but a double female bullet connector. I think this is the connection @SteveJ mentioned a couple of posts ago. I figured this out after looking at this 240Z Headlight-Wiper Switch Identification post and noticing there was a wire looping back on itself. It's always something simple.

Here are some detail shots:

  

 

Here's an updated diagram:

 

I also sort of answered my own question about the door switches. In the 1973 240z the driver's side door switch has three black wires coming off of it; one with a spade connector and two with bullet connectors. I don't know if other years are like this, but I have only found this three-wire switch once and it is very used. I may need to splice the missing wire onto one of the ubiquitous two-wire switches to make it work unless someone knows of an alternative part.

Edited January 21, 2023 by Matthew Abate

[SteveJ]

One of the connections on the driver door switch I think is for the key in ignition buzzer. (Mine works at random intervals.) One of the wires goes across to the passenger side to complete the path to ground for the door light when passenger door is open.

[Matthew Abate]

Right. And the third one goes to the steering lock switch.

Incidentally, I can't find a steering lock switch in all of my parts, and I can't find a photo of it online. I assumed (based on the diagram) that it is a separate switch from the ignition, because one of the 5 wires that comes from the back of the ignition goes to it. I also don't have either of the two buzzers nor the 2,200 Ω Resistor in any of my piles of stuff.

Edited January 21, 2023 by Matthew Abate

[SteveJ]

The steering lock switch is where you put the ignition key into. There have been threads about some newer switches lacking the wiring for the key in buzzer.

[Matthew Abate]

14 hours ago, SteveJ said:

The steering lock switch is where you put the ignition key into. There have been threads about some newer switches lacking the wiring for the key in buzzer.

Normally, this would make sense to me and is what I would have assumed before looking at the documentation from Nissan, but the wiring diagram in the FMS shows a Steering Lock Switch completely separate from the Ignition Switch:

The R wire goes to a splice connecting to the left side step light harness and the B wire is the third wire going to the left door switch illustrated in the post above. I have both of these wires in the harness on my table, but no switch that could be the STG LOCK SW in the FSM.

By the way, these R & B wires have no relationship to the Ignition Switch, so I am wondering if STG stands for something other than "Steering."

Edited January 22, 2023 by Matthew Abate