1973 240z Custom Wiring From Scratch

[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