SteveJ

I couldn't pull off the simulation well enough to suit me. First, look for corrosion. Where? Look at the PDF I attached. I indicated 4 areas to focus on, numbered in red. Inspection Points.pdf This is a visual inspection only. You're meter isn't designed to ferret out this kind of problem. For the fuse box, examine the contact points of the fuse holder, and you may need to remove the fuse box to examine the back side of it. Just be sure to pull the negative terminal off the battery before you attempt to do that. Sometimes disconnecting and reconnecting connectors cleans off enough corrosion that the circuit will work again. You may also want to try to jumper out the brake switch to see if that is the culprit. You can probably do that with a couple of bullet connectors and a short piece of wire.

Your results don't surprise me. In fact, it supports what I said in my previous post. You have a problem in the circuit that is restricting current flow between the battery and the turn signal switch. It won't show up as a problem using a voltmeter because the voltmeter is a high resistance device that doesn't require much current. The restriction shows up as a loss of voltage when the circuit is complete. It's late for me. I should have a chance to give you some more diagnostics tomorrow. Maybe I can even make a demo video to illustrate my point.

So now it's time to look upstream. I suspect you have some corrosion, poor connection, or a loose connection somewhere in the circuit. That improper current path is a choke point, and you see the voltage drop to nothing. You could try some things like jumpering out the brake switch and see if you have brake lights. Also measure the voltage to ground at the fuse for the brake circuit before and after connecting the turn signal switch.

Take some clear photos of the 6-pin connector on your turn signal switch so that we can see the wire colors. Also, when you plug the two halves of the connector together, look for movement in any of the wires. You might be pushing a wire out. If you had a good ground, you should have seen battery voltage to ground at the green/yellow wire.

Jumper these two wires together by using an inertia switch. Mount the switch securely to the dash. That will provide power to the fuel pump at key ON. The switch should cut power if you have an accident. I think the 6 pin connector is different from the one sold at Vintage Connections. I used some that I purchase on Mouser.com. Sorry, part number for the connector isn't readily available. If you want to get an non-generic inertia switch, you could get this: https://www.rockauto.com/en/moreinfo.php?pk=3970509&cc=1427576&pt=10756 and pair it with this connector: https://www.clipsandfasteners.com/Inertia-Fuel-Shut-Off-Switch-Harness-Connector-p/a23180.htm?gad_source=1&gclid=CjwKCAjwz42xBhB9EiwA48pT73NwDLlIv8yJGuM8TKHISt7fAUw23HCsEvFF2M9k7Fhdvmvwe0MfPhoCoIgQAvD_BwE You would want to fashion a bracket for it, though. Since it has normally open and normally closed contacts, you could wire it to a light to tell you if you need to reset the switch if it has been activated.

If the switch is disconnected from the brake pedal while the turn signal switch is in the neutral position, you should see 12VDC to ground at the points indicated below. If you don't, that means the switch was not rebuilt properly. Under those same conditions, you should have 12VDC to ground at the green wire in the picture above. Please confirm that.

Fuel pump power. What year is the 280Z?

You won't find a drop in condenser or drier. I haven't try to purchase either, so I cannot give you guidance. R12 is difficult to obtain since it was phased out over 30 years ago. It's probably smarter just to go with an R134a system while you're at it. Unfortunately I don't know a way to test the expansion valve in the existing evaporator. The expansion valve is another component that can fail and has no ready replacement.

Did you find an old JC Whitney catalog? I haven't looked at the modern systems, though your post prompted me to do a quick search. No real experience, but I haven't been motivated to look into doing it on either of my cars, yet.

I posted a short video of the use of a magnetic finger. I bought some a few years back, and sometimes I remember I have them. They can be handy for getting washers and fasteners into tight spaces.

Grommets, you say?

Talk to these guys. No personal experience, but they seem to have a following in GA. https://sixescustom.com/

Revisiting for clarity. The female YPC round terminals can be removed with a iwiss/icrimp weatherpack tool. The model number of the tool is WR01. I might have mentioned this elsewhere, but I thought it would be good to have the information reside here. It seems like the WR01 is only sold as a kit with a crimping tool or with other extractors. Frankly, the other extractors look like they would work on the YPC 6.3 and 2.8 mm connectors. https://www.amazon.com/IWISS-Extractor-Removal-Metri-Pack-Connectors-3/dp/B08PKLZXCX

Yes.

You can see me removing the clevis pin on the clutch pedal in this video. Here's a video of a bench I made to make it easier to get myself under the dash to reach up to things like the clevis pins. Also @Zed Head posted a tip many years back about how to use some thread to get the clevis pin back in. I think this may be it. And again here.

Well, eventually I might remember to try my experiment with a substitute. We can also double-check the wiring to see if there's something wrong. At least we know your wiper motor is good.

It's not too foolish to expect a new part to work. At least you had the good sense to examine the sending unit carefully, and you could fix it. Nope, not foolish.

Most of my getting into the doors has been to Work on door locks/latches Install door mirrors After taking off the door panel, chrome trim on the door, and upper window frame, I usually work the window out of the regulator. That involved moving the regulator up and down to get the rollers aligned. That may be tricky for you if the regulator is binding. I don't remember if I took out the regulator to clean/lubricate, but I never tried to take out the window with the regulator attached.

This may help, too.

They are NLA in the states. Are they available on your side of the pond?

Unless they changed things, Group Harrington bumpers are stainless.

Maybe something like these could be adapted. https://www.cjponyparts.com/cj-classic-trucks-windshield-washer-spray-nozzles-pair-chevrolet-c10-1960-1966/p/WWSN1/?year=1966&srsltid=AfmBOorzg5qObYNknNhDqvXyS_t8abztLRhItbJum_qInnfrWnpOpfubXSM This Mopar kit may have some potential, too. https://www.jegs.com/i/OER/691/K6671/10002/-1?srsltid=AfmBOoojCCedoDtafRJ2MaSH0UE_E_OP_mHOQiGg3JuaZmjOAOAouJVNd2o

I figured there was a good chance the tach would work. I learned about disconnecting the TIU a long time ago from reading about the ZX distributor swaps. It's common knowledge with us old farts who have been on this board forever. I actually had that come up about 10 years or so ago. A friend did the ZX distributor swap on another guy's car, and it ran like crap. He brought the car over to my place, and one of my first questions was about the TIU. He quickly disconnected it, and the problem was gone. I don't know how you have the CAS signal wired to the MS or what you did with the wires that the old distributor connected to, but somehow the TIU was getting a signal to ground out. That was what was messing you up. The tach doesn't really care too much about what device is grounding the coil negative to fire the plugs. It's basically just looking for that pulse.