1973 240z Custom Wiring From Scratch

[Matthew Abate]

Only 10A?

I’m thinking of splitting the 10 AWG white wire with a red stripe that comes from the alternator to the inside of the cabin. Originally it split off to the rear defroster and accessory relay, and terminated at the fuse box stud. The line going to the rear defroster had a 20A fuse on it originally.

The Koito H4 bulbs draw 10A each, and I’m retaining the long run of wires to the headlights that is in the engine harness to cut down on stuff outside of the cabin. Mainly I’m doing this relay mod to keep the power running through the combination switch as low as possible.

So what I’m thinking at the moment is splitting that 10 AWG white + red wire near the colored connectors and running it to the B post on the NLR-132. So there would still only be one wire coming off the alternator and feeding everything.

[SteveJ]

Are you keeping halogen bulbs? LED H4s will pull about 5A total from my measurements.

[Matthew Abate]

2 hours ago, SteveJ said:

Are you keeping halogen bulbs? LED H4s will pull about 5A total from my measurements.

Haven’t decided yet, but I want the option. I need to see how the LEDs perform before I commit, so if I don’t love them I would switch to H4.

[Matthew Abate]

Anyone have a source for the key warning buzzer and 3-wire door ajar switch for a 1973 240z?

I found a set but and hesitant due to price and unsure they even work.

I also have a workaround but am leaning OEM for now.

[Matthew Abate]

Can you guys help me figure out which relays I’m missing?

This is what I’ve found in my boxes:

1 - Horn Relay 26320-89905
2 - Defroster Relay 25230-N3000
3 - Thermostat Switch 22110-E8000
4 - Air Conditioner Relay 25230-89914 (the internet also says heater)
5 - Intermittent Relay 28820-N3300
6 - Fuel Pump Relay 25230-89915 (the internet also says headlight)
7 - Hazard Flasher (A & B not shown)
8 - Turn Signal Flasher
9 - Fuel Pump Relay 25235-P0101 (the internet also says fuse panel voltage regulator; I’ve seen a different relay with the same number)
10 - NLR-132 will be used for headlights

I have a key-warning buzzer coming in the mail for when the door is open and the key is in the on position. And I will not be using the Throttle Opener Relay that goes on the engine side of the firewall.

I have a 4-pin connector on the front fuel pump harness that I figure goes to a relay if you have an electric front fuel pump. I’m keeping my mechanical one for now because it is NOS. If it gives me issues I’ll switch over. I am assuming not having this connected doesn’t mess with anything since that was stashed away with blue tape from the factory.

I’ve also seen things about a “heater / choke” relay, but don’t see anything for that in the diagram. I found a relay numbered 25235-P0110 on a Datsun 1200 wiki, but can’t find anything for Z cars.

—-

I think I’m all set. I don’t think I need to retain the thermostat switch (#3). I think this might be unique to 1973-4 automatics.

Can anyone identify that thing or think of anything I might be missing?

Edited March 18 by Matthew Abate

[Matthew Abate]

I’m not 100% certain all of these relays are good (still testing), but I cleaned up the best looking pieces from my pile assembled them today. 🤞🏻

[Matthew Abate]

I’m hoping someone can clarify some things for me:

I would like to put something approximating the “correct” capacitor (aka condenser) on my coil and wire it up as original if possible.

Z Car Depot describes the RFI suppression capacitor as plugging into the harness via a bullet connector.

My harness was cut at several points because the previous owner was trying to force an AT harness to work in a manual, so I may have made a mistake when mapping everything to the wiring diagram.

There is a B/W wire that splices to a green wire that ran to the voltage regulator and then through the firewall and to the green wires coming off the fuse box that supply power to the seatbelt switches & light and gauges.

Could this B/W wire be what is supposed to connect to the capacitor? If so, that makes it easy. If not, I’ll just use it as an aux power feed and tape it back for any future needs.

Secondly, is that even the best way to wire it up? I know others wire it directly to the positive pole on the coil.

And last, does it matter what capacitance rating I use for this? The 280ZX (my engine and ignition are from a ZX) used a two-wire, 250v, .47uF capacitor. I have no idea what the 240z used. As far as I can tell, the .22uF ones were for the dizzy.

I’ve found one from an RX-7 that has that rating, but it doesn’t look anything like the cylindrical ones from the ‘70s. I’ve also found some that are .50uF. Is that difference going to impact anything?

Maybe this is trivial and I’m overthinking it, but like I said, I’d like to at least try to get it right.

Edited May 24 by Matthew Abate