1973 240z Custom Wiring From Scratch

[Matthew Abate]

I have decided that the wiring on my '73 is going to be complicated enough to warrant it's own build thread. I will post the high level stuff in the full-car build thread (https://www.classiczcars.com/forums/topic/51541-1973-rebuild/#comments), but the details and back and forth conversation will be here.

This is going to be a huge learning process for me since I have no experience in this area.

With that said, this is where I am with this so far…

When I got the car, the harnesses were installed, but the car was otherwise stripped. I pulled the harnesses, gave them a cursory dusting off and stuffed them into a box. The dash harness is still on the dashboard, which is on a shelf.

I have been tracking an inventory of modifications I want to make to my electrical system over the past few years as I work on the rest of the car. I had a lot of ambition when I first put this list together, but I have backed off from my initial list of additional components over time. This is what I am still thinking about doing:

• Anti-Theft Kit / Alarm (Mostly because I have one laying around that I never installed on my motorcycle)
• Auxiliary Fuse Box or an Upgraded Fuse Box
• Bluetooth Speaker
• Electric Radiator Fan, plus maybe a thermostat controlled switch that would allow it to run after to car is turned off.
• GPS
• Third Brake Light
• Under Dash / Footwell Lights
• USB Socket / Phone Charger
• LED Exterior Lights
• 100-Amp Alternator
• Radio Delete
• LED Headlights
• Rally / Fog Lights
• 12-volt Socket (Replaces Cigarette Lighter)
• Door / Step Lights (These are super rare and way too expensive)

Other Considerations…

• Figure out where I am going to do this work (it's getting hot)
• Decide which type of wire for each component (TXL, SXL, GXL, etc.)
• Choose connectors (Original style?, Deutsch style?, AMP style?, Weatherpack style?)
• Decide which colors to use for each color in the original harnesses
• Find amperage / voltage / wattage for each component
• Determine ideal wire size for each component
• Choose distributor
• Choose fuse box, distribution block, relay upgrades
• Identify fuse and relay requirements for each component
• Draw up new / modified wiring diagram
• Choose wrapping material
• Find shrink-wrap labels for label maker
• Find retailers

___

Right now I have a pretty solid spreadsheet put together with all of the components I need, mapped to the wiring diagram, and tracking the parts I plan to buy.

 

Oh, and I’ve never done automotive wiring before, so this will be an experience.

Edited June 21, 2022 by Matthew Abate

[SteveJ]

Fuse size depends the gauge of the wire you're protecting. I recommend 10A for 14 AWG, 20A for 10 AWG or 12AWG and 7.5A for 16 AWG or 18 AWG. Don't forget about maxifuses or fusible links for the system as a whole.

As I searched for vendors for wires with colored stripes, I found this place was probably about the most economical and flexible: https://www.sherco-auto.com/striped-tracer-wire.html

You may be able to adapt this for fusible links: https://www.amazon.com/1J0937617D-Battery-Terminal-Volkswagen-Octavia/dp/B0863XLF6R

As for current draw, let the factory fuse box be your guide to start. 

The fan is the highest draw, especially if you have AC. While the parking/tail light fuse is 20A, you can go to 10A and 14 AWG with LEDs. (IMHO the engineers undersized the wire in this circuit for incandescent bulbs.) The same goes for the flasher. The Common fuse is for the cigarette lighter. That can drop to 10A. I'm not positive about the draw on the wipers, but if you keep it at 20A, I would use 12 AWG instead of 14 AWG. The brake light circuit can also go to 10A with LEDs. Note: the fuse ratings I wrote are very much on the conservative side. However, I have seen enough melted fuse boxes and melted connectors that I prefer a conservative approach.

As for wire sizes here is a rule of thumb.

The wires for the large connectors should be 14 AWG. Use 16 AWG for the smaller connectors. On the 73 (and on through 76), Nissan started using the 9 pin connector on the headlight switch. That was a bad move. The connectors were undersized for the current of the parking lights, and that connector would melt down.

For the large bullets, I would use 10 AWG. Consider trying 8 AWG for the circuits for the ammeter.  Are you sticking with the ammeter or are you going to have a voltmeter instead?

[Matthew Abate]

Thanks @SteveJ!

I think you already noticed this based on your comments, but I'll state it for anyone else who may comment: My overall goal in this is to make the ideal wiring system for the car with consideration to the modifications I am going to make, not to replicate the original. That said, I don't want to deviate wildly from original because I want to be able to go back and fix stuff if necessary. I also want to reduce complexity and weight wherever possible.

However, I also think I will go heavier than necessary with the wiring so I never have to worry about that part of the system. The things on the ends of the wires are a lot easier to fix down the road than the wires themselves.

___

Here is my first pass at an inventory of components for this project, sorted according to their position in the wiring diagram:

Mod	Item	Replacement	In Diagram?
Stock	Antenna Lead	Delete	Yes
Stock	Antenna Lead	Delete	Yes
Stock	Water tank		Yes
Upgrade	Side Marker Lamp RH	LED Bulb - Front Turn Signal	Yes
Upgrade	Inspection Light	LED Bulb - Inspection Light	Yes
Stock	Horn Relay		Yes
Stock	Battery		Yes
Stock	Accessory Relay		Yes
Stock	Choke Switch		Yes
Upgrade	Map Light	LED Bulb - Map Light	Yes
Stock	Rheostat		Yes
Stock	Fuel Pump		Yes
Stock	Defrost Relay		Yes
Upgrade	Glove Box Light	LED Bulb - Glove Box Light	Yes
Upgrade	Room Light	LED Bulb - Dome Light	Yes
Upgrade	Room Light		Yes
Stock	Tank Unit		Yes
Stock	Step Light RH		Yes
Upgrade	Side Marker RH	LED Bulb - Red Marker Light	Yes
Upgrade	Rear Combination Light RH	LED Bulb - Brake Light	Yes
Upgrade	Rear Combination Light RH	LED Bulb - Rear Turn Signal	Yes
Upgrade	Rear Combination Light RH	LED Bulb - Reverse Light	Yes
Upgrade	License Light RH	LED Bulb - Plate Light	Yes
Upgrade	License Light LH	LED Bulb - Plate Light	Yes
Stock	Heat - Glass		Yes
Upgrade	Rear Combination Light LH	LED Bulb - Brake Light	Yes
Upgrade	Rear Combination Light LH	LED Bulb - Rear Turn Signal	Yes
Upgrade	Rear Combination Light LH	LED Bulb - Reverse Light	Yes
Stock	Auto Antenna	Delete	Yes
Stock	Antenna switch	Repurpose ???	Yes
Stock	Side Marker LH		Yes
Stock	Step Light LH		Yes
Stock	Comb. Switch		Yes
Stock	Hand Break Switch		Yes
Stock	Speedometer		Yes
Stock	Tachometer		Yes
Stock	Oil Pressure / Water Temp		Yes
Stock	Fuel Gauge / Ammeter	Voltmeter	Yes
Stock	Clock		Yes
Stock	Choke Warning Light		Yes
Stock	Defrost Switch		Yes
Stock	Seatbelt Warning Light		Yes
Stock	Fog Light Switch		Yes
Stock	Door Switch RH		Yes
Upgrade	Cigarette Lighter	12 volt plug	Yes
Stock	Seat Switch		Yes
Stock	Seatbelt Switch LH		Yes
Stock	Seatbelt Switch RH		Yes
Stock	Neutral Switch		Yes
Stock	Buzzer		Yes
Stock	Door Switch LH		Yes
Stock	Indicator Lamp (Auto T/M)		Yes
Stock	Hazard Switch		Yes
Stock	Ignition Switch		Yes
Stock	Steering Lock Switch		Yes
Stock	Wiper Motor	91 Honda Civic Wiper Motor	Yes
Addition	Wiper Motor	Wiper Upgrade Relay	No
Stock	Buzzer		Yes
Stock	Inhibitor Switch (Auto T/M)		Yes
Stock	Air Con Power		Yes
Addition	Air Conditioner		No
Stock	Blower Switch		Yes
Stock	Heater / Blower		Yes
Upgrade	Side Marker Lamp LH	LED Bulb - Front Turn Signal	Yes
Addition	Side Marker Lamp LH	Side Marker LED Conversion Plugs	No
Stock	Parking & T/S & Side Front LH		Yes
Upgrade	Head Light LH	Headlight Projection Housings	Yes
Upgrade	Head Light LH	Headlight Projection Housings	Yes
Stock	Horn L		Yes
Stock	Fog Light LH		Yes
Stock	Fog Light RH		Yes
Addition	Front Fog / Rally Light Relay		No
Stock	Horn R		Yes
Upgrade	Head Light RH	Headlight Projection Housings	Yes
Upgrade	Head Light RH	Headlight Projection Housings	Yes
Addition	Head Light RH	Headlight Relay Upgrade Harness	No
Upgrade	Parking & T/S & Side Front RH	LED Bulb - Front Turn Signal	Yes
Addition	Parking & T/S & Side Front RH	Parking Light Upgrade Harness	No
Addition	Parking & T/S & Side Front RH	Parking Light Upgrade Harness, 70-73	No
Stock	Volt Reg		Yes
Stock	Voltage Regulator		Yes
Stock	Thermal T/M		Yes
Stock	Oil Pressure		Yes
Upgrade	Fuse Box	280ZX Fuse Box	Yes
Upgrade	Fuse Box	Long Pigtail Blade Style Fuse Box	Yes
Upgrade	Fuse Box	Short Pigtail-Blade Style Fuse Box	Yes
Upgrade	Fuse Box	Short Pigtail-Blade Style Fuse Box	Yes
Upgrade	Starter Motor	Gear Reduced Starter Motor	Yes
Stock	Fusable Link	Circuit Breaker / Fuse	Yes
Upgrade	Radio	Stereo Delete Box	Yes
Stock	Reverse Switch		Yes
Stock	T/S Flash SW		Yes
Stock	Four Way Flasher		Yes
Stock	Brake Ind.		Yes
Stock	Ballast Resistor	Delete ???	Yes
Stock	Stop Sw		Yes
Stock	Thermo sw (Auto T/m)		Yes
Upgrade	Alternator	Alternator - 100 Amp	Yes
Addition	Alternator	Alternator Upgrade Plug	No
Stock	Fusable Link	Circuit Breaker / Fuse	Yes
Stock	Thermo Relay (Auto T/M0		Yes
Stock	Coil		Yes
Stock	Distributor (Manual T/M)		Yes
Stock	Distributor Condenser		No
Addition	Anti-Theft Kit / Alarm		N/A
Addition	Auxiliary Fuse Box		N/A
Addition	Bluetooth Speaker Power		N/A
Addition	Electric Radiator Fan		N/A
Addition	Electric Radiator Fan Pigtail		N/A
Addition	Electric Radiator Fan Temp Control Kit		N/A
Addition	GPS Power		N/A
Addition	Third Brake Light		N/A
Addition	Under Dash / Footwell Lights		N/A
Addition	USB Socket / Phone Charger		N/A
Upgrade	LED Bulb - Dashboard Light Set		N/A
Stock	Fuel Sender Electrical Connector		No
Stock	Electric Fuel Pump Wiring Install Kit Harness Relay		No

 

@SteveJ, I don't know if I will be going with the ammeter I have or converting to a voltmeter. I need to look at the pros and cons of that change. In fact, I have not decided if I am keeping the factory gauges at all. This is a restomod and I have already made irreversible changes, so I don't know. I might also address the 9-pin switch by backdating that to an earlier version.

 

Any suggestions on other changes anyone has that will make the car better would be much appreciated. I am hoping this thread can turn into a resource for others and not just me tracking my progress.

Edited June 5, 2022 by Matthew Abate

[zKars]

A wonderful and admirable project. 

My thoughts.

ditch the ammeter, voltmeter only. No need to have lots of high current wire running around with no purpose. and go aftermarket gauges without doubt. Don’t forget the AFR gauge as well. Vendors make 3d printed adapters for speedhut gauges for S30’s.

Join the world of Deutsch connectors and/or weatherpack. Relatively small investments and easy to crimp and make waterproof connections. Like the brake line world, once you invest in the tooling (good pair of crimpers), all wiring issues become simple to handle rather than a pain in the, well you know.  

Since you still need to interface to OEM components, vintageconnections.com has many of the stock pins and connector shells you need. 

[Matthew Abate]

Thanks @zKars! I'll take your comments into account. I was already leaning toward Deutsch or Weatherpack connectors. The gauges I had not considered changing due to the lack of dual options out there, but I'll look around.

In addition to suggestions for adding or swapping things, if anyone sees anything on my list that they think I should take off, please let me know. For example, I had someone tell me to ditch the electric fan and keep the original, but I am not sure about that because I am going to add air conditioning.

Edited June 5, 2022 by Matthew Abate

[Barefootdan]

I used weather pack in my harness and I’d recommend them. Easy to crimp and pin…and de-pin! The only downside to them is they’re bulky. I used the 280 series if I recall correctly and the 6 pin isn’t small. I do know they have slimmer series though up to 12 pin I believe. But for the large bulkhead connectors I used a molex style. Deutsch has some nice connectors, especially if you want the whole chassis to be the same connector style. Definitely get a quality crimper!!
 

For wiring I went GXL. I felt it provided sufficient coverage for regular driving. 11 colors was enough diversity for me to not get mixed up. But I did remove alot of the OEM options (door lights, buzzers, safety, etc). Wirebarn was a good source for this. 
 

Check out my build thread for more details on it and feel free to ask any questions! 

[Matthew Abate]

I went through the wiring diagram I have, which I downloaded from this site, and captured the wire colors running to each component in the stock system. I am planning to use this list to figure out what color wire to change to when I am unable to source wiring in the stock colors, but I thought I would post it here for anyone who wants it.

Item	OEM Wire Color
Water tank	• Black • Black w/ Yellow
Side Marker Lamp RH	• Black • Green w/ Blue
Inspection Light	• Ground • Red w/ Blue
Horn Relay	• Green • Green w/ Black • Green w/ Red
Battery	• Black • Black • Ground
Accessory Relay	• Blue • Black • White w/ Red • Blue
Choke Switch	• Black • Red w/ Blue
Map Light	• Black • Red w/ Blue
Rheostat	• Green w/ White • Red w/ Blue
Fuel Pump	• Yellow • Black
Defrost Relay	• Blue w/ Red • Black • White w/ Red • Red w/ Black
Glove Box Light	• Ground • Red w/ Blue
Room Light	• Black • Red w/ Blue
Tank Unit	• Yellow • Black
Step Light RH	• Black • Red w/ Blue
Side Marker RH	• Black • Green w/ White
Ground	• Black
Rear Combination Light RH	• White w/ Black • Green w/ White • Black • Red w/ Black
Rear Combination Light RH
Rear Combination Light RH
License Light RH	• Black • Black
License Light LH	• Black • Black
Heat - Glass	• Red w/ Black • Black
Rear Combination Light LH	• White w/ Black • Green w/ White • Black • Red w/ Black
Rear Combination Light LH
Rear Combination Light LH
Auto Antenna	• Blue w/ Red • Blue w/ White • Black • Antenna Lead
Antenna switch	• Blue w/ Red • Blue w/ White • Blue
Side Marker LH	• Black • Green w/ White
Step Light LH	• Black • Red w/ Blue
Comb. Switch	• Green w/ Blue (1) • Green w/ White (2) • White w/ Red (19) • Black (3) • Blue w/ Yellow (4) • Blue w/ White (5) • Red (20) • Blue (6) • Red w/ Blue (7) • Blue w/ Red (8) --- • Green w/ Yellow (9) • White w/ Red (10) • White w/ Black (11) • Green w/ Red (12) • Green w/ Black (13) • White (14) • Red w/ White (15) • Red w/ Black (16) • _____ (17) • Green w/ Black (18)
Hand Break Switch	• Ground • Yellow w/ Blue
Speedometer	• Red w/ Blue • Red w/ Blue • Red • Red w/ White • Yellow w/ Blue • Red w/ Blue
Tachometer	• Green • Red w/ Blue • Green w/ Black • Green w/ White • Black w/ White • Green w/ Red • Red w/ Blue • Black
Oil Pressure / Water Temp	• Black • Yellow w/ White • Green to Yellow w/ Red • Red w/ Blue • Green to Yellow w/ Red • Yellow w/ White
Fuel Gauge / Ammeter	• White w/ Red • White • Red w/ Blue • Yellow • Green to Yellow w/ Red • Black
Clock	• Black • Red w/ Blue • Blue
Choke Warning Light	• Red w/ Blue • Red
Defrost Switch	• [MISSING] • Blue w/ Red • Blue
Seatbelt Warning Light	• Black • Green
Fog Light Switch	• Red • Red w/ Green
Door Switch RH	• Black • Black • Ground
Cigarette Lighter	• Blue w/ White • Black
Seat Switch	• Red • Green w/ Black
Seatbelt Switch LH	• Green w/ Black • Green
Seatbelt Switch RH	• Green • Green w/ Black
Neutral Switch	• Green • Green
Buzzer	• Green • Black
Door Switch LH	• Black • Black • Black • Black • Ground
Indicator Lamp (Auto T/M)	• Black • Red w/ Blue
Hazard Switch	• Green w/ White (1) • Green w/ Red (2) • Green w/ Black (3) • Green (4) • Green (5) • Green w/ Yellow (6) • Green w/ Yellow (7) • White w/ Black (8) • White w/ Red (9)
Ignition Switch	• Black w/ Yellow (1) • Black w/ White (2) • White w/ Red (3) • Blue w/ Red (4) • Green w/ Blue (5)
Steering Lock Switch	• Red • Black
Wiper Motor	• Black (E) • Blue w/ Red (B) • Blue (L) • Blue w/ White (M) • Blue w/ Yellow (H)
Buzzer	• Yellow • Red
Inhibitor Switch (Auto T/M)	• Black w/ Yellow • Black w/ Yellow • Red w/ Black • Red
Air Con Power	• Red to Blue
Blower Switch	• Red • Black • Black
Heater / Blower	• Red • Black • Black • Ground
Side Marker Lamp LH	• Black • Green w/ Blue
Parking & T/S & Side Front LH	• Black • Green w/ Red • Green w/ Blue
Head Light LH	• Red w/ Black • Red w/ White • Red w/ Yellow
Horn L	• Green • Ground
Fog Light LH	• Black • Red
Fog Light RH	• Black • Red
Horn R	• Green • Ground
Head Light RH	• Red w/ Black • Red w/ White • Red w/ Yellow
Parking & T/S & Side Front RH	• Black • Green w/ Blue • Green w/ Black
Voltage Regulator	• Black (E) • White (A) • White w/ Black (F) • Yellow (N) • _____ (L) • _____ (–) • Black w/ White (IG)
Thermal T/M	• Yellow w/ White • Ground
Oil Pressure	• Yellow w/ White • Ground
Fuse Box	• Green w/ Red (H) • Green w/ Yellow (S) • Red w/ Blue (PT) • Red w/ Blue (PL) • Red (HR) • Red w/ Yellow (HL) • Blue w/ White (C) • Blue (A) • Blue w/ Red (W) • _____ (F) • Black w/ White (IG) • Blue w/ Red (C) • _____ (–) • _____ (–) • _____ (–) • Red (–) • White w/ Red (A) • White w/ Red (A) • _____ (–) • White (B)
Starter Motor	• Black • Black • Black w/ Yellow • Ground
Fusable Link	• Black
Radio	• Ground • Black • Red w/ Blue • Antenna Lead
Reverse Switch	• Red w/ Black • Red
Turn Signal Flash Switch	• Green • White
Four Way Flasher	• Blue w/ White • Green w/ White
Brake Indicator	• Yellow w/ Blue • Ground
Stop Switch	• Green w/ Yellow • Green w/ Yellow
Ballast Resistor	• Green w/ White • Black w/ White
Thermo sw (Auto T/m)	• Black w/ White • Green
Alternator	• Black (E) • _____ (A) • White w/ Black (F) • Yellow (N) • _____ (–) • _____ (–) • _____ (–) • _____ (–) • _____ (–) • _____ (–) • Fusible Link (A) • Black (E)
Fusable Link	• White w/ Red
Thermo Relay (Auto T/M0	• Green • Black • Black • Red w/ Black to Black
Coil	• Black • (To Distributor)
Distributor (Manual T/M)	• Black • (From Coil)

[Matthew Abate]

Also, I found this helpful in understanding what we are dealing with here: 

 

[Matthew Abate]

I have some noob questions maybe some of you can help me out with:

Is it better to build the wiring for mods into the main body harness or make a separate one that attaches to the main one, given I am starting from scratch?

Can I somehow repurpose the Thermo Switch / Thermo Relay for an automatic transmission to control my electric radiator fan?

Could I repurpose the wires for the automatic antenna and antenna switch for anything, like power for a Bluetooth speaker, for example?

Could I repurpose the wires for the Inhibitor switch for an automatic transmission for anything?

Could I repurpose the wires for the indicator lamp for an automatic transmission for anything?

Edited June 16, 2022 by Matthew Abate

[scotta]

If I was to rewire a car I would be looking to use a PDM - power distribution module also called PMU. They are a solid state device that simplifies wiring and does away with the traditional fuses. it allows for peak current management, retries if current exceeded, logic, timers, etc. There are a few on the market. If you were also going to change the gauges, look at CANbus gauges. They can integrate with the PMU.

The PMU would also allow you to change inputs and outputs so you could repurpose beore or after installed.

 

The PDU's cost a bit but you save on wiring and the time to install. 

https://www.ecumaster.com.au/products/ecumaster-pmu

The PMU route is a bit of a rabbit hole as is CANbus, but does modernise the entire setup.

[Matthew Abate]

This is super cool! It also sort of negates the reason I got a 240z, which is to have a car with no computer that I can fix myself. It also costs 2/3rds what the car cost me.

I am looking at going with a more modern ignition system though…

[Matthew Abate]

Okay. Made a nail board…

It’s flimsy and probably too small, but it fits in my home office so I can theoretically work on this when it’s crazy hot out. I’m hoping that makes the project more likely to move forward.

Edited June 18, 2022 by Matthew Abate

[Matthew Abate]

Okay, the body harness has been stripped.

 

I am very glad I didn’t try to use this thing. It’s melted / burnt in two places and has been messed with and rewrapped in three places. The next step is to compare this to the diagram and see what the story is.

[Matthew Abate]

I just learned something that is not immediately obvious to someone who has never done this kind of thing before: The positions and lengths of the lines in the wiring diagram DO NOT correspond to my harness very closely at all.

Yes, the wires connecting one component to another are captured in the diagram, but there is no relationship between either the length or the proximity of one wire to another in that diagram to what is in the car.

What I mean by this is the just because two wires are next to each other in the diagram does not mean they are in a same harness. The best example of this are the blue/white and blue/red wires that go from the antenna switch to the antenna. In the diagram these are very short and not near anything else. These two wires are the longest wires in my body harness, where they are twisted up with 18 other wires.

There is also a random blue wire in the 1973 diagram coming from the Accessory Relay and going to nothing. It goes between the two flashers in the dash and just stops in the empty space.

Just a word of caution to anyone else jumping into their first wiring project with both feet. They’re great for checking wire colors but you need a physical representation to refer to in order to make a new harness.

Edited June 19, 2022 by Matthew Abate

[Patcon]

Yes, that is normally true of this type of wiring diagram

[Matthew Abate]

Okay, my plans suffered their first casualty: I will not be going with an electric compressor on my AC system. It’s possible, but I would need to have a 200 amp alternator to handle the draw. The one I have is 100 and can’t cover it. I would also have to figure out some kind of controller to make sure it was operating and cycling correctly, and I’m trying to avoid computers. The thing that really tipped it over the edge, though, is having to move it out of the engine bay to keep it cool. These things are too big and need pipes to the condenser, even if you move the condenser somewhere too, so there isn’t an obvious place to put it.

So that simplifies my project a little. I can probably pull the trigger on my AC parts now.

—-

I think I want to have my additional interior components on a new / additional harness. I haven’t decided if it would attach to the body harness or the dash harness yet, but it is for my additional power supplies to charge phones and a Bluetooth speaker. At least two of them will be USB-C plugs, and the last either a 12-volt plug or another USB-C.

Edited June 21, 2022 by Matthew Abate

[Matthew Abate]

I have verified that is is the right harness for my car by the part number printed on the white shrink near the blue clip (24014-n3300). It isn't the one that came with the car, which I can tell because it has metallic green overspray on it and I am pretty sure my car never had. I think it is for a 7/72 to 7/73 car, which mine is (7/73), but it has the black connector sleeves for the defroster, which came on the 75-83 harnesses according to Banzai Motorworks.

I still have two things I have not been able to figure out about this harness, though:

1. This one is minor. The room light wires should be Red w/ Blue, Black, and Black. I have 3 long wires that I know are for the room light based on the connectors on the ends, but they are Red w/ Blue, Black, and Red w/ Black. Is this maybe just a foible of my harness? I know these aren't mixed up with the defroster wires because I have accounted for those and verified them by the connectors on those wires, even though they are the same colors. This would not be the only place where the wire colors deviate from the diagram. The rear combination light connectors don't match the diagram either, but they do match the FSM.

 

2. This one is perplexing. I have two wires (White & White w/ Black stripe) coming out of the harness at the same point as the two wires that go to the left rear marker light. I haven't been able to find these in any of the wiring diagrams for any year.

As far as I can tell, these do not go to the tail lights, license plate lights, fuel pump or sensor, antenna, or marker lights. Is this maybe a European, Canadian, Californian, or Right-Hand-Drive harness? Some of the diagrams specify market-specific options and others are USA only. They do have the same connectors as the Step Light wires on the other end of the harness, but that runs into the door from the front on the right side. The left door switch is on the dash harness, plus the connectors don't match, so it isn't that. Maybe rear fog lights (not in the diagram)?

I'm pretty sure that these supply signal and power to the speaker that was in the left rear quarter panel.

 

Any help figuring this out would be much appreciated!

Edited June 23, 2022 by Matthew Abate

[Matthew Abate]

I have a question about these plugs on the body harness:

The one at the top of the photo is to the fuel pump and is labeled in the wiring diagram and the FSM. It has two wires (black, yellow) and two plugs in a T arrangement.

The other on is the one I can’t identify. It has one plug and one wire (green) that is a heavier gauge than all of the other wires in the harness. The connector has a tooth for a clip and the wire goes all the way back to the blue 10-pin connector that joins the dashboard harness.

I checked the FSM and don’t see a label for this wire where it describes that blue connector, but it is directly across from the yellow wire in that connector, which goes to the fuel pump.

Is this just a third wire for that fuel pump harness? If so I wonder why they didn’t just use a 3-plug connector. Is it for the fuel tank sending unit? That is showing as two wires (black, yellow) in the diagram.

 

Edited June 25, 2022 by Matthew Abate

[SteveJ]

Yellow and black = Fuel sending unit.

Green = fuel pump power.

[Matthew Abate]

4 hours ago, SteveJ said:

Yellow and black = Fuel sending unit.

Green = fuel pump power.

Awesome! Thank you.

I just realized I may have filed this thread in the wrong place. I don’t see an electrical section but maybe one of the moderators can move it to the right place.

Edited June 26, 2022 by Matthew Abate

[Matthew Abate]

Finished the inventory of the body harness…

 

Tagged all the connectors and checked them against the diagram. Measured the lengths and identified all of the splice points.

Here’s everything I’ll need to replicate it (except the optimal wire gauge), with the splice color indicating the color tape covering the splice:

1973 240z Body Harness Inventory
Position	Component	Conector Color	Connector Style	Connector Image	Direction	# of Pins	# of Wires	Diagram Wire Color	Harness Wire Color	Min. Feet of Wire Needed
1	Instrument Harness A	Blue	10-Prong		F	10	10	White w/ Black	White w/ Black	[See Speaker]
								Blue w/ Red	Blue w/ Red	[See Antenna]
								White	White	[See Speaker]
								Blue w/ White	Blue w/ White	[See Antenna]
								Yellow	Yellow	[See Fuel Pump]
								Green w/ Black	Green w/ Black	[R. Comb. Lamp RH]
								Green w/ Red	Green w/ Red	[R. Comb. Lamp LH]
								Green	Green	[See Belt Switches]
								Green	Green	[See Seat Switch]
								Green	Green (Heavy)	[See Fuel Pump]
2	Instrument Harness B	White	6-Prong		M	6	6	Red w/ Black	Red w/ Black (Thick)	[See Rear Glass Defroster]
								Red w/ Blue	Red w/ Blue	[See Room Light]
								Yellow w/ Green	Yellow w/ Green	[See Hand Brake Switch]
								Green w/ White	Green w/ White	18 (to Green Splice C)
								Red w/ Black	Red w/ Black	[R. Comb. Lamp LH]
								Black	Black	1 (to Yellow Splice)
3	Door Switch	Clear	Spade		F	2	2	Black	Black	[See Step Light Harness]
								Black	Red w/ Black	[See Room Light]
4	Step Light Harness	Clear	Bullet		M	1	1	Black	Black	2
		Clear	Bullet		F	1	1	Red w/ Blue	Red w/ Blue	1
4	Yellow Splice	N/A	N/A	N/A	N/A	2	2	Red w/ Blue	Red w/ Blue	N/A
								Black	Black
5	Hand Brake	Clear	Spade		F	1	1	Yellow w/ Green	Yellow w/ Green	8
6	Green Splice A	N/A	N/A	N/A	N/A	3	3	Green	Green	N/A
								Green	Green
								Green	Green
7	Belt Switch RH	White	3-Prong Mini		F	3	2	Green w/ Black	Green w/ Black	[See Seat Switch]
								Green	Green	7
7	Green Splice B	N/A	N/A	N/A	N/A	3	3	Green	Green	N/A
								Green w/ Black	Green w/ Black
8	Seat Switch	White	3-Prong Mini		F	3	2	Green w/ Black	Green w/ Black	1
								Red	Green	1 (from Green Splice A)
9	Belt Switch LH	White	3-Prong Mini		F	3	2	Green w/ Black	Green w/ Black	1 (from Green Splice B)
								Green	Green	12
9	White Splice A	N/A	N/A	N/A	N/A	2	2	Black	Black	N/A
								Black	Black
10	Room Light	Clear	Spade		F	1	1	Black	Black	3 (from White Splice A)
		Clear	Spade		F	1	1	Red w/ Blue	Red w/ Black	17
		Black	Spade		M	1	1	–	Red w/ Blue	17
11	Rear Glass Defroster	Black	Spade		F	1	1	Black	Black	19
		Black	Spade		F	1	1	Red w/ Black	Red w/ Black	15
12	Green Splice C	N/A	N/A	N/A	N/A	3	3	Green w/ White	Green w/ White	N/A
								Green w/ White	Green w/ White
12	Rear Side Marker Light RH	Clear	Bullet		M	1	1	Black	Black	1 (from White Splice B )
		Clear	Bullet		F	1	1	Green w/ White	Green w/ White	1 (from Green Splice D)
13	Tank Sending Unit	White	2-Prong w/ Clip		F	2	2	Black	Black	6 (from White Splice A)
								Yellow	Yellow	14
	Fuel Pump	White	1-Prong		F	1	1	Black	Green	14
								Yellow	–	–
14	Rear Combo Lamp RH	White	4-prong Small		F	4	4	Black	Black	3 (to White Splice A)
								White w/ Black	Green w/ Black	16
								Green w/ White	Green w/ White	2 (to Green Splice E)
								Red w/ Black	Red w/ Black	1 (to Green Splice D)
14	Green Splice D	N/A	N/A	N/A	N/A	2	2	Red w/ Black	Red w/ Black	N/A
								Red w/ Black	Red w/ Black
15	Green Splice E	N/A	N/A	N/A	N/A	3	3	Green w/ White	Green w/ White	N/A
								Green w/ White	Green w/ White
								Green w/ White	Green w/ White
								Green w/ White	Green w/ White
15	License Plate Light	Clear	Bullet		M	1	1	Black	Black	2 (to White Splice B )
		Clear	Bullet		F	1	1	Black	Green w/ White	1 (from Green Splice E)
16	Rear Combo Lamp LH	White	4-prong Small		F	4	4	Black	Black	1 (to White Splice B )
								White w/ Black	Green w/ Red	18
								Green w/ White	Green w/ White	1 (from Green Splice E)
								Red w/ Black	Red w/ Black	18
16	White Splice B	N/A	N/A	N/A	N/A	2	2	Black	Black	N/A
								Black	Black
								Black	Black
								Black	Black
17	Side Marker Light LH	Clear	Bullet		M	1	1	Black	Black	2 (from White Splice B )
		Clear	Bullet		F	1	1	Green w/ White	Green w/ Black	3 (from Green Splice E)
18	Speaker	Clear	Bullet		M	1	1	–	White w/ Black	19
		Clear	Bullet		F	1	1	–	White	19
19	Antenna	Clear	Bullet		F	1	1	Blue w/ Red	Blue w/ Red	20
		Clear	Bullet		F	1	1	Blue w/ White	Blue w/ White	20

Edited July 12, 2022 by Matthew Abate

[Matthew Abate]

You may have noticed a few things I marked in Red in the last post. These were wires that differed from what I have in the Factory loom I disassembled in the wiring diagram. Well, I have a few more for the engine bay. I still have a lot of wire chasing and investigation to do, but I can point out two things:

1. The Throttle Opener Relay is missing from the wiring diagram I downloaded, but it is in the FSM wiring diagram for 1973 cars with manual transmissions (bottom left hand corner near the coil).

2. The 10-pin clips are differing pretty substantially this time. I am not surprised by a couple of wires being different colors, but also, the White and Black connectors are swapped from what is in the FSM and I am missing a wire in each of the other two. I need to find out somehow if these were removed or just never there in the first place. Maybe this will become apparent after I finish chasing the wires.

Component	Connector Color	Connector Style	Direction	# of Pins	# of Wires	Diagram Wire Color	Sample Wire Color
Instrument Harness A	Blue	10-Prong	F	10	9	Red w/ Black	Red w/ Black
						Red w/ White	Red w/ White (Heavy)
						Green w/ Black	Green w/ Black
						Green w/ Red	Green w/ Red
						–	–
						Yellow w/ Green	Yellow w/ Green
						Red w/ Black	Red w/ Black
						Black w/ Yellow	–
						Red	Red
						Blue w/ Yellow	Blue w/ White
Instrument Harness B	Green	10-Prong	F	10	8	Black	Black
						Black	Black (Heavy)
						Green w/ Black	–
						–	–
						–	–
						Green w/ Black	Green w/ Black
						Green w/ Red	Green w/ Red
						Blue	Black w/ Yellow
						Green	Green
						Green	Green
Instrument Harness C	White Black	10-Prong	F	10	8	Yellow w/ Green	Yellow w/ Green
						Blue	Blue
						Black	Black
						–	–
						–	–
						Red w/ Yellow	Red w/ Yellow
						Red w/ Blue	Red w/ Blue
						Green w/ Blue	Green w/ Blue
						Red	Red
						Blue w/ Yellow	Blue w/ Yellow
Instrument Harness D	Black White	10-Prong	F	10	9	Green w/ White	Green w/ White
						Black w/ White	Black
						White	White
						Green	Green
						–	–
						Yellow w/ White	Yellow w/ White
						Black w/ White	Black w/ White
						Black w/ White	Black w/ White
						Yellow w/ Blue	Yellow w/ Black
						Yellow w/ Red	Blue w/ Red

Edited July 12, 2022 by Matthew Abate

[Matthew Abate]

Well, I am pretty sure that my engine harness is for an automatic, not the manual harness I need.

It has a 6-prong plug (G, B, B, BY, BY, BY) and a long branch with a yellow/blue wire. In the diagram that wire goes to the inhibitor. Both of these are automatic only.

Not a crisis, because it was damaged and messed with in a number of places, but it does make using this as a guide to build my new one significantly harder.

Edited June 29, 2022 by Matthew Abate

[Matthew Abate]

Okay, I officially need help. I have 14 wires in this harness I cannot identify at all, and 5 that I think I have right but am not 100% sure about.

Starting at where this harness connects to the dashboard harness, here is a list of what I have identified already:

• Instrument Harness A through D, To Dash Harness A from Alternator, To Dash Instrument Harness B from Starter Motor, Horn Relay, Intermittent Relay, and Hazard
• Wiper Motor
• Starter Motor, and Starter Ground
• Oil Pressure Switch, Alternator, and Alternator Ground
• Voltage Regulator and Condenser
• Inspection Light
• Side Marker Lamp RH, Parking & T/S & Side Front RH, Head Light RH, Fog Light RH, and Horn RH
• Horn LH, Fog Light LH, Parking & T/S & Side Front LH, Head Light LH, and Side Marker Lamp LH

---

So, working from the end furthest from the firewall toward the dashboard connectors, this is what I am looking at:

• I have a yellow wire ending in a female bullet connector sharing a sleeve with a black wire ending in a female spade connector
• That black wire extends to where the yellow wire merges into the harness and has another female spade connector
• At that same point I have a green w/ white wire and a black w/ white wire, both ending in female spade connectors
• There is also a longer black w/ white wire ending in a female spade connector and shrouded in a black sleeve

 

Further up the harness, about 10 inches from the bundle of wires for the lights on the left side of the car, I have 3 wires that have been cut: black w/ yellow, green, and black. See the far left side of the following image.

 

The next mystery is a bundle of 4 wires that emerges between the bundle for the starter and the thick branch of wires that holds the wiper motor connector, among others. There are 2 red w/ black ending in male bullet connectors and 2 black w/ yellow ending in female bullet connectors. See the middle of the image below.

(Also, can someone confirm that that is the water tank wire?)

 

Lastly, I have two 4 wires emerging from that thick branch that holds the wiper motor connector and what I think is the seatbelt relay (automatic only). There is a black wire that is on its own and has been cut. There is also a bundle of 3 wires: black ending in a male spade connector, black w/ yellow ending in a female spade connector, and yellow with green ending in a female bullet connector. This bundle of wires is about 6 1/2 feet long, and the diagram does not show any yellow w/ green wires.

(Can someone confirm that that is the seat belt relay connector?)

---

So yeah. That's the hangup on finishing this step of the project. If anyone has any idea what these wires are for, please let me know. It is entirely possible that these were modifications the previous owner made, but I am hopeful that we can solve this collectively.

Edited June 29, 2022 by Matthew Abate

[SteveJ]

39 minutes ago, Matthew Abate said:

• I have a yellow wire ending in a female bullet connector sharing a sleeve with a black wire ending in a female spade connector
• That black wire extends to where the yellow wire merges into the harness and has another female spade connector
• At that same point I have a green w/ white wire and a black w/ white wire, both ending in female spade connectors
• There is also a longer black w/ white wire ending in a female spade connector and shrouded in a black sleeve

Yellow - connects to the temp sender

Black - goes from the distributor to coil negative

Green/white - from ballast resistor to tachometer

Black/white - from key switch (ignition power) to ballast resistor

Black/white with shroud - from tachometer to coil positive

44 minutes ago, Matthew Abate said:

Further up the harness, about 10 inches from the bundle of wires for the lights on the left side of the car, I have 3 wires that have been cut: black w/ yellow, green, and black. See the far left side of the following image.

Black/yellow & black - washer motor

Green - typically horn

58 minutes ago, Matthew Abate said:

The next mystery is a bundle of 4 wires that emerges between the bundle for the starter and the thick branch of wires that holds the wiper motor connector, among others. There are 2 red w/ black ending in male bullet connectors and 2 black w/ yellow ending in female bullet connectors. See the middle of the image below

Red/black - reverse light switch on transmission

Black/yellow - neutral safety switch for solenoid power

1 hour ago, Matthew Abate said:

Lastly, I have two 4 wires emerging from that thick branch that holds the wiper motor connector and what I think is the seatbelt relay (automatic only). There is a black wire that is on its own and has been cut. There is also a bundle of 3 wires: black ending in a male spade connector, black w/ yellow ending in a female spade connector, and yellow with green ending in a female bullet connector. This bundle of wires is about 6 1/2 feet long, and the diagram does not show any yellow w/ green wires.

The black was probably a ground - maybe the chassis ground?

Black/yellow - solenoid power

Yellow/green - not sure why this would be alone. It could be associated with the intermittent wiper relay. Page BE-2 does show the Y/G wire as a pin on a 3 wire connector. The mystery is that BE-2 shows 2 Y/G wires for the engine harness. One is on the blue connector, and the other is on the white connector. However, I only can find the destination of one Y/G wire at the 3 wire connector.