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