1973 240z Custom Wiring From Scratch

[Matthew Abate]

Okay, I made some progress over the weekend.

I pulled the gauges and ducts out of the dashboard last week, so I had access to all of the wiring, which is now out.

 

I also purchased a Volt / Fuel gauge for a 1975-76 280z. These had the same condensed font as the 240z, so it should look like it’s supposed to be there. I’ll have to take note of this when I draw up the new wiring diagram.

I also investigated getting a 280z tach, as we discussed previously. Originally I thought I would be able to put a ZX tach instrument into the tach housing because of a video I saw claiming this can be done, but he must have misspoken because the ZX instrument is pretty different and doesn’t just bolt in the way a 280z tach instrument does.

I’m thinking about doing this because I went ahead and bought that 280zx distributor with the E12-80 module on it.

I think the best course of action, although a little on the spendy side, is to find a good 280z tach and swap the instrument into my housing. This will be another place where I need to change the wiring diagram, particularly because of the 2200 ohm resistor required.

So now on to cataloging this dashboard harness.

[siteunseen]

I can say that I have an OE '72 240Z tach that works as it should with an E12-80 ZX distributor. "I" did it myself from "Blues tech tips" without any problems. I'm stressing that I did it, you're way deeper than I ever could be and without walking downstairs I'm almost positive my 240 has more of a block style numbering than my 280.

You can do it. 🙂

[Matthew Abate]

@siteunseen, you mean this, right?

http://www.atlanticz.ca/zclub/techtips/distributor/index.html

[siteunseen]

1 minute ago, Matthew Abate said:

@siteunseen, you mean this, right?

http://www.atlanticz.ca/zclub/techtips/distributor/index.html

Yes sir. I found the crane fireball p20, I believe, has the right ohms.

This mostly...

 

[siteunseen]

I think this plug made my work so simple. I got it off a junkyard ZX here, local. Really clean and simple, hidden inside wire moulding.

 

And it is a PS 20 coil.

Here's the speedos in my cars. 280 first...

240...

 

 

 

[Matthew Abate]

Okay, so it’s the COIL that determines if the tach works correctly in the 240z. So why do I keep reading that the electronic ignition screws that up?

Whatever! If my tach will work then I’ll keep it. The issue is that I don’t want to have to take it out once it’s in. Hard enough getting it out with the dash out. I can’t imagine pulling one from a complete car.

[SteveJ]

There a lot of people posting that something doesn't work because they don't know how to diagnose the system to find the real problem. See "firing the parts cannon."

[Matthew Abate]

I'm deep in the process of cataloging the dashboard harness and it's making me lean toward trying to use OEM connectors, rather than modernizing the harnesses with new technology (although I am open to hearing arguments against this). The one place I think this is going to be super challenging is with the big 10-pin connectors that come in blue, green, white, and black and join the individual harnesses together.

Does anyone have an idea of whether or not these can be found new or NOS anywhere? I haven't seen them anywhere, whereas I have been able to find pretty much all of the other connectors used in these harnesses somewhere.

Edited August 5, 2022 by Matthew Abate

[SteveJ]

This isn't color coded, but here are 10 pin latching connectors: https://www.ebay.com/itm/251571360455 Also here: https://www.aliexpress.com/item/2251832114000835.html?gatewayAdapt=4itemAdapt and here: https://www.amazon.com/DJJ7021F-6-3-11-Electrical-Connectors-Automobile-Connector/dp/B07WQWMMLT?th=1

Choice #2, back out the pins and re-use the shells.

[zKars]

First, I am very impressed at your ambition trying to renew the harness. I have re-furbished many harnesses, but tend to just replace pins and sometimes connector shells, never all the wire as well. Rarely is the wire compromised unless I find corrosion in the strands as I replace terminals. High current wires, (ie the fat white ones) I commonly replace entirely including all ring and connector terminals. 

These fancy colored 10 pin 73 specific connectors have the same 6.3mm spade terminals as the other 2/4/6 pin connectors, so just remove each terminal, inspect clean or replace it, and snap it back in the housing. No need to replace the housings, which you can’t do any way, they are not available new. 

You can use Weatherpack or Deutsch connectors (DTM for 14gage and higher, DT for 10-12).

 Steve’s suggestion for 10 pin connectors are fine, but I’d just do terminal service and retain the stock housings. 

[Matthew Abate]

Thanks for the advice guys!

I’ve been talking to Vintage Connections about their 240z kit, which they claim contains all the connectors I’ll need for the car. I think I am going to get it if it is accurate to my inventory. I’ll report on that later.

For the 10-pin clips, I may reuse the one I have, but I’m going to see if I can figure out an alternative before I decide.

@zKars I was going to try to reuse these, but after I stripped the wrapping off I found so many bad splices, burnt through wires, corrosion/oxidation, cut wires, and other issues I decided to rebuild from scratch. Plus, the engine harness isn’t even the right one, being for an automatic, and I have numerous components to add or remove.

I honestly think it’s going to be less work to make fresh harnesses.

Edited August 8, 2022 by Matthew Abate

[Matthew Abate]

Okay, this one is going to be a long one, so I will try to bust it up into pieces to keep the conversation organized, because the dash harness (or harnesses, as it turns out) was a doozy. In one way it wasn't as tricky as the engine, because it is the correct harness for the car this time, but it was trickier in another way in that there were few things I could identify before I disconnected them (being disconnected when I bought the car) and the ones with spade and bullet connectors are not in the FSM Body Electrical section, so I am juggling between several years of FSM, the diagrams I downloaded here, and lots of Google searches.

For the purpose of clear communication I will refer to both of these harnesses as halves of the larger "dash harness." If I need to distinguish between them I will refer to the one with all of the lightbulbs as harness #2 and the other one as harness #1, since their part numbers are 24013-M3322 and 24013-M3321, respectively.

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@SteveJ, @zKars, @Zed Head, and everyone else, I am hoping to enlist your help in identifying at least some of the things I couldn't figure out so I can fill in the blanks in the table. Hopefully some of you will know what these should be.

Condenders are the 4-way flasher, heater, air conditioning power, resistor, fog light switch, and wiper motor.

 

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Missing Wires:

In capturing the wire mapping from the FSM, I found that my harness is missing a black wire with a yellow stripe from the blue connector, and a black wire from the green connector (not the heavier gauge wire that goes to the combination switch).

After reviewing the FSM and the diagram, the only black and yellow wire running through the dashboard I see is the one from the ignition to the starter (via the inhibitor switch in automatic cars). I have accounted for that one and it is in a different connector.

The black one could be anything, really. I don't have any black wires missing on the other ends that I can tell.

 

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Unidentified Connectors

#1 & 2: There are several places there the two harnesses connect to each other via bullet connectors. I have figured out what almost all of the bullet connector are throughout the whole harness except for a few on each half. OF the first two, one is a male bullet on the end of a 3-inch blue wire with a red stripe exiting Intermittent Relay plug.

The other one is a female bullet also on a blue wire with a red stripe going to the fuse box.

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#3 (Harness 1): Next is a 3-pin connector with 3 wires (White w/ Black, White, Blue) on the branch that goes down the center console to the fuse box. The blue wire has a blue sleeve on it that may or may not be a repair from the previous owner.

This one is right next to the connector for the antenna motor (left side of the photo above), so I thought this might be for the radio, but I have that one accounted for. There is no component on the wiring diagram with this combination of wire colors, as far as I can tell.

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#4 (Harness 1): This one might be power for the Air Conditioning, or it could be for the heater. There is a blue wire branching off the 30-amp fuse in the diagram for that. The trouble is, that fuse should have a red wire coming off it for the blower fan, but I am not seeing that in this mess.

I think this one is for the heater.

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#5 (Harness 1): Another truly perplexing one is this 3-prong clip with two black and one green wire. This exits the center-console branch along with the ones above, but it's about a foot long. No idea what this is. it's missing in the FSM and the diagram, and I don't see a component with this color combination.

I think this one is for the buzzer.

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#6 (Harness 1): There is a blue wire with a white stripe right next to the connectors for the fuse box. I think maybe this one is for the four-way flasher, but I am not certain.

This is for the fuse box.

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#7 (Harness 1): This 2-prong connector is down the console near the choke and seat belt lights. Wires are black with a white stripe and green.

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#8 (Harness 2): Again, on the branch going down to the fuse box, this time on the other half, there is a blue wire with a female bullet connector. Maybe this connects to the other stray blue with I thought was for the AC, or maybe this is for the heater. I have a feeling these two are for those two components, it's just a question of which is which.

I think this one is for the AC.

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#9 & 10 (Harness 2): These last two are also on the fuse-box branch. One is a thicker white wire with a sheath and a female bullet connector (middle wire in the photo below), which should make it easy to identify, but I'm still confused. This one splices to the fat wire that goes from the engine harness to the Ammeter.

This is also for the fuse box.

The last thing I can't figure out is the 2-prong connector is the photo above. It is not in the FSM and I can't find a component in the diagram with this combination. Maybe it goes to the resistor, because I do have an unaccounted for black & white wire that I mentioned earlier on the other fuse-box branch, but they are both paired with other wires (green / red) that are not showing in the diagram for that component, so I don't think so.

 

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Anyway, that's what I have to figure out before I can wrap up this inventory. One thing all the Googling I've been doing is teaching me is there are a bunch of little harnesses I might be missing. I already know about the tail light, fuel pump, headlight, turn signal, and step light harnesses, but I just saw a center console harness I haven't seen before on eBay (may be for a 280z ¯\_(ツ)_/¯ ). After this one I'll do the fuel pump harnesses and research the others. Then I can move on to deciding which materials to buy to make the new one.

Thanks in advance for any help.

Edited August 19, 2022 by Matthew Abate