1973 240z Custom Wiring From Scratch

[SteveJ]

18 minutes ago, Matthew Abate said:

Thanks. I will read up on them.

As I am working in integrating my ZX distributor into my wiring, I noticed quite a few threads here and over at Hybridz where people say you can live without the condenser that is NLA for those cars. This was the 2-wire condenser that plugged into a wire coming out of the distributor on one end and spliced into the BW wire going to the electronic ignition on the other. I'm also noticing that in the ZX the condenser joins up to wires going to the fuel pump and the ignition switch, whereas the 240z has the condenser on a wire that goes to the seat switches, fuse box, hazard switch and some gauges. Curious if anyone has any thoughts on this.

Right now I am leaning toward keeping the 240z setup for that specific component.

The condenser at the distributor was to help reduce the voltage spikes on the points. The ZX distributor doesn't have points, hence the lack of a need for the condenser. The one at the alternator is to reduce noise for things like your radio.

I'm not sure about what condenser you're talking about for the other components. Where do you see this?

[Matthew Abate]

1 hour ago, SteveJ said:

The condenser at the distributor was to help reduce the voltage spikes on the points. The ZX distributor doesn't have points, hence the lack of a need for the condenser. The one at the alternator is to reduce noise for things like your radio.

I'm not sure about what condenser you're talking about for the other components. Where do you see this?

The ZX had two as well, even though it didn't have points; one on the alternator and an RF interference condenser on the distributor. It didn't connect to the coil but it did connect to the ignition switch.

 

Edited March 2, 2023 by Matthew Abate

[Matthew Abate]

Made a little bit of progress yesterday on my electric fan set up. The main "Ah ha!" moment that I had one I can simplify things by adding an auxiliary fuse box. I know adding an additional component sound like making this more complex, not simpler, but what I realized is that all of my new components in the engine bay could be fed off that Aux fuse box. The only two things I am adding up front are the air conditioning system and the electric radiator fans, which means the wiring from the engine harness to that fuse box can be pretty simple.

Components for the electric radiator fan are:

• 1 x Fan thermostat switch (I am looking into using the two-wire 280ZX switch at the water neck for this)
• 2 x Fan Relay
• 2 x Circuit Breaker
• 2 x Electric Fan

Components under the hood for the air conditioning are:

• Air Compressor
• AC Trinary Switch (automatically shuts off the air-conditioning clutch if the refrigerant pressure gets too high / low)
• A/C Compressor Low Idle Control
• Idle Adjustment Solenoid

The thing I am trying to figure out now is if the AC components should be wired to the Accessory position on the key, or if they can be on the On position. The fans will be on the On position. It's not a big deal either way, but I want to talk to Vintage Air about it tomorrow to see what they say about it. The evaporator and thermostat switch in the dash are both already on the Accessory position.

Now to find a fuse box.

[SteveJ]

I bought a few of these to play around with. https://www.amazon.com/dp/B09VK1WYVP

I found the harness to plug into it on Aliexpress and bought a few, too. 

[Matthew Abate]

4 minutes ago, SteveJ said:

I bought a few of these to play around with. https://www.amazon.com/dp/B09VK1WYVP

I found the harness to plug into it on Aliexpress and bought a few, too. 

Thanks! I was just looking at that. I also found one for a Nissan Juke I am considering. The overlanding / off-roading community seems that have a bunch of stuff in this space. Must be for all those light bars.

Edited March 5, 2023 by Matthew Abate

[Matthew Abate]

I've been working on some detail illustrations for the individual component modifications that I am making to these harnesses. First up are the ignition and the volt meter. I have been able to find good documentation, including diagrams of the wiring, of how these two modifications are supposed to be done, so I was able to consolidate all of that and add some details based on the work I have been doing in the harness diagrams.

240z e12-80 Ignition & Distributor Wiring Modification:

This ignition setup is pretty straight forward and has been documented repeatedly in several places, but I have found some details about how the 280zx distributor is set up in its factory setup in a 1979 ZX, specifically the condenser. There are tons of components that tie into the wires that connect to the ignition that simply don't exist in the 1970-78 cars.

I am guessing (since people have been able to make this setup work in Z cars) this doesn't impact anything, but it does make me take a pause when I am trying to be thorough and have a clean harness when I am finished. I plan to dig into this a little deeper, but I have reassurance from a couple people in this thread and my main build thread that this setup works without requiring any other mods, such as the 280z tachometer swap and/or adding a 2.2k ohm resistor or a MSA HI-6 box.

 

240z Volt Meter Wiring Modification:

The volt meter I have is from a 1976 280z. I chose this one because the face is closest to the 1973 ammeter as far as the typography and graphics are concerned. It's not a match, but it's close enough that it looks like it could have been in the car original. The 1977-8 volt meter has completely different lettering and looks like a mistake.

I'm relying heavily on the information @tamo3 and @EuroDat posted in this thread where @tamo3 showed how he modified a 1977 voltmeter to fit into a 1975 280z. It's pretty clear, but I am planning to modify it further because the 1973 combination switch doesn't connect to the ammeter like it does in the 1975.

The only hesitation I have on how I have drawn this up is the illumination light. In the 240z you have a single wire light that grounds to the instrument case. in the 280z you have the 2-wire lights that connect directly the common ground throughout the wiring. I am pretty sure but not 100% sure this will still work because the case is grounded via the black wire on the 4-pin connector that goes to the fuel pump.

Edited March 8, 2023 by Matthew Abate

[EuroDat]

You might want to read the other thread Tamo had. He did more upgrades and included more photos of the voltage meter as well.

 

[Matthew Abate]

On 3/8/2023 at 5:40 PM, EuroDat said:

You might want to read the other thread Tamo had. He did more upgrades and included more photos of the voltage meter as well.

Thanks. I've dug through everything and it looks like I am good to go with this voltmeter.

 

***

 

I've started working on adapting my Vintage Air Gen II Mini air conditioner to the dash harnesses. One thing I just noticed today is they have two wires coming into it from the car: one from the battery (30 amps) and one from the ignition (5 amps). Both of these go to a relay that goes to the fan switch and a second relay that feeds the blower on the evaporator.

https://www.vintageair.com/instructions_pdf/MINI GEN II HCD WIRING DIAGRAM.pdf

I am wondering if I need this relay because I have the power coming off the accessory relay, which is on the ignition switch already. In theory I could just remove the relay Vintage Air has in their wiring and connect it into the power that used to feed the heater blower. It just feels like an extra relay that isn't needed.

Or am I missing something and I need a separate wire from the ignition that isn't going through the accessory relay?

Thoughts?

 

Edited March 9, 2023 by Matthew Abate

[billgtp]

I used both of the vintage relays in my harness. I did not do an amp or volt test on the Vintage blower  motor  to see if I could wire from the accessory relay in my car.  I made a relay and power box for the car to house them all in the engine compartment. Maybe the pictures will give you some ideas

Also I used a 280z thermostat housing for the temp. sensors.

 

[Matthew Abate]

Thanks for the tips @billgtp! I will file this away for later.

Right now I am working on switching out the 240z turn signal switch in my diagram for one from a 260z. This mod will also involve changing the rail lights to the euro configuration. Here's the main guide I am looking at. I will be doing the same thing as the guide I am using for reference by creating an interim harness that adapts the 260z switch to the 240z dash harness.

My first issue is that I made a few errors in my first diagram where I had the front turn signals going to the pin for the rear signals, and vice versa. That has been fixed. My second issue is that the tail lights all ground to the fuel tank sending unit. I need to go back to the harnesses and make sure that is correct. A quick look at the FSM tells me it is, but I am not 100% certain, given the number of other errors I found in that thing.

As noted in the guide above, the 260z does not send the brake signal through the turn signal switch, so I have to figure out how that is supposed to be wired in those cars. The rest of it seems pretty straight forward, though.

Here's a diagram of the two switches:

In the 240z, #9 is the signal coming from the brake switch. In the 260z, the #9 is in neither the combo switch (wiper switch) nor the TS switch, so I am looking at where it goes. #10 through #14 are consolidated in the 260z.

Another thing I noticed is that the  tail light harnesses I got from Z Car Depot each has a socket for a dual-filament bulb where the red wire is cut and knotted. These are brand new, so I need to look into what that is for. Once I find my old ones I should be able to make a comparison and see what is up. Its a little bit of a pain because the wires switch colors underneath the wrap and have no relationship to the FSM. Fun times.

***

I know it seems like I am jumping around, but I'm finding that these different sections impact each other in that I have to route wires for the new components through the colored connectors at the bulkhead, so I think it is better that I resolve all of the swaps before I resolve the additions.

Edited March 18, 2023 by Matthew Abate

[Matthew Abate]

Finished drawing up the wiring change for the tail lights:

[Matthew Abate]

After a long hiatus due to the layoff apocalypse in the tech industry I’m back on this.

I just purchase the 240z kit from Vintage Connections. It’s not exactly right for a ‘73 240z but it’s close and I can probably use the extra bits for my electric fans and the like. I’m going to have to reuse my colored connectors that join the harnesses to each other, since those are NLA.

As for the wire itself, I’m going to take @SteveJ’s advice and go with the marine-grade striped wire from Sherco. It’s a step up from the standard automotive wire I had been looking at, plus I can stick to the factory wire color combinations.

I’m mostly done with the modifications to my wiring diagram, with the exception of the changes to the tail lights I mentioned previously and the third brake light, as well as the 12-volt socket to replace the cigar lighter and the USB-C plugs I want to add. Should be simple.

Oh, and I realized that I had been making the volt meter modification too complicated. If I retain the ammeter wiring and splice in a thin wire for the volt meter I’ll have the perfect setup for a kill switch. I will I se that switch to join the white and white / red wires (rather than splicing them) and relocate all of that down to the lower part of the dash or center console to mount the switch. Easy Peezy, in theory.

Edited May 19, 2023 by Matthew Abate