SteveJ

See if there are markings on the flasher unit near the terminals. If you see an L, that is the terminal for the green/white wire. The worst case scenario is that you put the wires on and test your hazard lights. If they don't work, flip the wires around on the flasher relay.

Just to reduce redundancy: https://www.zcar.com/threads/fan-blower-and-ac-have-quit.427939

It means your battery isn't up to the task of powering those things at the same time. Before you're ready to fire up your engine, get your battery tested (and possibly replaced).

If you've seen issues with the wiring around the ammeter, that could be contributing to the issue you are seeing. When the car isn't running, the power for all of the circuits except horn, brake lights, and hazard lights travels through the ammeter. If the connections at the ammeter are heating up (higher resistance), that can drop the voltage.

That fuse that suffered the meltdown is for the parking light circuit. The fuse for the radio is on the top right. It's on the same circuit as the blower motor. Put a 10A battery tender on the car and run the test again. For the melting down fuse, you may want to look into the Motorsport Auto fuse box replacement. It should be listed on this page, but it just keeps blanking out on me: https://www.thezstore.com/category/543/fuse-amp-relay-boxes The wire sizing for the parking lot circuit was marginal at best for a 20A circuit. You can get that circuit down to about 1A by changing all of the gauge bulbs and exterior bulbs to LED.

Look for corrosion around your fuse box, especially underneath.

I'll test it again after the home projects are done. There's too much chaos until all of the furniture gets moved back in (hopefully on Wednesday).

I haven't had issues with the Vintage Connections open barrel terminals. What crimpers are you using? This is the one I use. It has a die for open barrel terminals. https://www.amazon.com/dp/B0BJVH4J6Q @Yarb has a set, too, but just with the D die (open barrel).

RL & RB together - Defrost switch (My assumption from looking at the 72 wiring diagram...I can't find the switch on the 70 or 71 wiring diagrams.) RL in center - maybe radio light @Captain Obvious was trying to update the wiring diagram for the 70 a couple of years ago. I don't know if he ever "finalized" the product to his satisfaction.

I'm not sure what relay you could be talking about. The black/yellow wire is the circuit that energizes the solenoid. In a manual car, it's a home-run from the key switch to the solenoid. If you're running the engine harness I worked on, I know that was an automatic transmission harness, so it had the break in the circuit for the neutral safety switch on the transmission. All I did was join the two wire ends together essentially making the starting circuit wired like a manual transmission circuit. The only place it could get power would be from the key switch unless there are some modifications in the dash harness on that car.

Off hand, I can't think of where the problem could be outside of the switch.

Resurrected Classics has a reproduction hose set now. I have a set waiting to go into the 73. https://resurrectedclassics.com/collections/weatherstrip-and-rubber/products/gas-tank-vapor-hose-set-for-240z-260z-1970-1974-datsun

I took the 260Z out to a car meet this morning. The nice thing is that it ended before the temperature got to the ludicrous zone.

Which relay, and which wire? Keep in mind that the problem could still be upstream of where you found it. Corrosion at the splices is a real thing in a car that's about 50 years old.

Are you running an electric fuel pump or a mechanical? I use the 0-30 PSI gauge from this brand in my fuel injected 260Z to monitor fuel pressure - https://www.maxtow.com/black-green-maxtow-15-psi-fuel-pressure-gauge/

Well, if you're not trying to match the original, you might find something here: https://www.mcmaster.com/products/bumpers/system-of-measurement~metric/ Also, look at the results of this google search: https://www.google.com/search?q=metric+stopper+bolt+with+bumper&sca_esv=63ec7e79828cdf8c&biw=1920&bih=911&sxsrf=APpeQnsq13L7bEDRQtXSUDrClx_F-hUqCw%3A1783112014069&ei=TiFIasLjA-D-p84PhOSlEQ&ved=0ahUKEwjCwsXxsbeVAxVg_8kDHQRyKQIQ4dUDCBA&uact=5&oq=metric+stopper+bolt+with+bumper&gs_lp=Egxnd3Mtd2l6LXNlcnAiH21ldHJpYyBzdG9wcGVyIGJvbHQgd2l0aCBidW1wZXIyBRAAGO8FMggQABiABBiiBDIFEAAY7wUyBRAAGO8FSPsZUM4PWLsXcAF4AZABAJgBrgGgAbkGqgEDMi41uAEDyAEA-AEBmAIIoALJBsICChAAGEcY1gQYsAPCAgcQABiABBgNmAMAiAYBkAYCkgcDMS43oAfQE7IHAzAuN7gHxwbCBwMyLjbIBwqACAE&sclient=gws-wiz-serp

The relay in the link is a horn relay. If the device @Warty is referring to is marked the same, he has found his horn relay. To answer the question not asked: H gets the solid green wire that goes out to the horns. B gets the green/red wire that should have 12VDC+ S gets the green/black wire that goes to the steering column for the horn button.

I suggest you follow down the line to see where you're getting the voltage drop. You should be able to get a meter lead in the backside of the connectors.

No, it is not normal. I suggest looking for corrosion in the connectors in the fuel pump circuit. Don't forget to check the EFI relay and Ignition relay. The relays and the contacts associated with them could cause a voltage drop.

I didn't crack open the 75 FSM to compare, but this is in the 76 FSM. It looks like the water temperature switch was removed and the coolant bypass was installed in it's place. Where does the wire go to that is attached to the sensor on the side (where it should be the coolant bypass)?

Reach out to Junkyard Jenny.

Yes, I own that one. It functions much like the Power Probe, but it costs less.

Here's another one. I haven't see the Fluke 88V near this price in over 6 years: https://www.amazon.com/Fluke-88V-1000V-Automotive-Multimeter/dp/B000WTB67K That one will do most anything you need a multimeter to do on a car, including dwell angle (calculated from duty cycle). There are also other Fluke multimeters on sale. They aren't cheap, but I'm still using a Fluke I got around 25 years ago. The Autel PowerScan is a Prime Day deal, too - https://www.amazon.com/Autel-Automotive-Electrical-Resistance-Continuity/dp/B0BW48DKFG You can use it to measure voltage and even energize a circuit. That can be handy for diagnosing a circuit.

Here are a couple of deals on products that I own and like: Haisstronica ratcheting crimpers with various dies - https://www.amazon.com/haisstronica-6PCS-Crimping-Tool-Non-Insulated/dp/B0BJVH4J6Q I've used those a lot on open barrel terminals (6.35mm, 2.8mm, YPC). They also work well crimping the metal splices I have used in repairing wiring. TopDon thermal camera - https://www.amazon.com/TOPDON-TC004-Mini-Handheld-Resolution/dp/B0F29969G1 I almost forgot to add this toolset that I got to throw in the back of my Z or carry in my truck - https://www.amazon.com/GEARWRENCH-Piece-Mobile-Tech-GWCBMTS54P/dp/B0G5YS9JKQ

The blue/white wire is connected to the wire that goes out to the washer pump. In the wiring diagram, that wire is labelled as black/yellow. However, I do not have first hand knowledge if that is correct. You should look for a female bullet connector in the dash harness at the steering column that is not solid black. The wire should be the same gauge as the blue/white wire.