SteveJ

Okay, your car probably has the fuel pump relay modification. It looks like you have two wires at the starter solenoid. There is no need to cut any wires! Just unplug Relay A. The relay is located on the passenger kick panel. If the relay is plugged in and you have that alternator mod, you will run your battery down.

Measure voltage to ground on the backside of the connector. One pin should have voltage with the engine off. That is the battery sense. Also, look to see if the connector is corroded.

But have you checked battery sense voltage at the alternator?

Yes. For the 78 it's easier than for earlier S30s since your car is already set up for an internally regulated alternator.

It has to be a 4 cylinder Frontier or Xterra to have the correct pulley.

I haven't had any issues with the Frontier alternator I bought from Rockauto. https://www.rockauto.com/en/moreinfo.php?pk=8829284&cc=1359200&pt=2412 Rockauto has several other brands listed as new (not reman). You also have to buy a plug like this to integrate it into the wiring. https://www.amazon.com/gp/product/B07ZMN2B59 Attach that plug to a 2 pin connector from Vintage Connections (http://www.vintageconnections.com/Products/Detail/79), and you can plug the new alternator into your car. Last, but not least, you'll need to replace the ring on the alternator charge wire with one that can go on the M8 post on the alternator.

There is only 1 bid on record for that username (for that "engine") and no comments on record. It can make a reasonable person wonder.

The main reason behind the recommendation for marine wire was they seemed to have every combo needed. I actually found a site last night that has GXL wire with tracers, but they don't have every color combo needed for the Z. Here's an updated list for wire colors: BR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_BLACK_W_RED_STRIPE_p/gxl-14awg-0103.htm BW https://www.sherco-auto.com/striped-tinned-tracer-primary-wire-14-ga-x-25-ft-black-wwhite-stripe-25-ft-usa-made-for-marine-and-automotive-use-also-in-25-ft-rolls.html BY https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0105.htm GB https://www.sherco-auto.com/striped-tinned-copper-tracer-primary-14-ga-x-25-ft-coil-green-wire-black-stripe-usa-made.html GL https://www.sherco-auto.com/primary-tracer-marine-tinned-copper-14-gauge-awg-x-25-ft-coil-green-wire-blue-striped-usa.html GR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0403.htm LW https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0702.htm LY https://www.sherco-auto.com/striped-tinned-tracer-primary-14-ga-x-25-ft-coil-blue-wire-yellow-stripe-usa-made.html RB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0301.htm RB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0301.htm RL https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0307.htm RW https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0302.htm RY https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0305.htm YB https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0501.htm YG https://www.sherco-auto.com/striped-tinned-tracer-primary-14-ga-x-25-ft-coil-yellow-wire-green-stripe-usa-made.html YR https://www.acdcwireandsupply.com/GXL_14_AWG_AUTOMOTIVE_WIRE_STRIPE_p/gxl-14awg-0503.htm YW https://www.sherco-auto.com/primary-tracer-marine-tinned-copper-14-gauge-awg-x-25-ft-coil-yellow-wire-white-striped-usa.html B https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-01.htm G https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-04.htm L https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-07.htm R https://www.acdcwireandsupply.com/Gxl_Automotive_Wire_p/gxl-14g-03.htm

Now I have a few minutes for the long-form answer. For the 240Z, the ammeter measured the full current between the battery and the ammeter. If there was a short in that area, the full ammeter current would feed the fault. The battery was limited by the fusible link. (Don't be fooled, while the FSM wiring diagram shows a fusible link off the alternator, I've never seen a car equipped with one.) Also, if the ammeter failed, the car was dead. If it was running when the ammeter failed, it might keep running, but as soon as you turn it off, the car would not restart since the battery was now isolated from the majority of the electrical system. For the 260Z, the design was improved by using a shunt to limit the current flowing through the ammeter. Also the failure of the ammeter would not strand the car. Less of a fire hazard and eliminated a single point of failure. That's definitely an improvement. The 75 carried on this design, and the 76 introduced the voltmeter.

The shunt is for the Ammeter.

I've never had the opportunity to tear into the wiring of a 75, but I strongly suspect that the interlock relay has been completely disabled. Ford developed the seatbelt interlock relay and presented to the NHTSA in the early 70s. The bureaucrats thought that it was the perfect solution for getting people to wear their seatbelts, so they quickly added it to the regulations for the 74 MY cars. This meant all of the other automakers selling cars in the US had to come up with their own interlock schemes and QUICK. Many of the implementations left a lot to be desired. I remember my older brother figuring out how to disable it in our family's 74 Impala. Faced with a litany of complaints along the lines of cars not starting unless the bag of groceries was buckled safely for the trip home, the NHTSA quickly unwound the requirements. Most automakers were even quicker about removing these bastard implementations. However, documentation is usually the last thing the engineering team wants to address, and I'm betting all of the proofs were already completed for the service manuals for the already delayed debut of the 280Z before they got yanked. If the interlock relay did ever exist in a production 75, I would expect it would have the emergency bypass switch like what the 260Z had. More useless trivia: The switch was moved between the early and late 260Zs. On the early (first 12 months) car, the switch is on the right fender, near the battery. On the late (last few months) car, the switch is mounted on the firewall.

Back in the car meet swing with a fully operational Death Star...er, I mean 260Z. Does this count as a Z31 showing up? It was having an out-of-body experience.

This can be useful for early Z cars that don't have a voltmeter: https://www.amazon.com/gp/product/B01M9IKYVH Did the fuse for the fan survive this event? It about sounds like you might have a short in that circuit.

The sender for the water temp on my cars have a bullet connector. Anyway, the crimp on that female bullet connector can be subject to wear from the wires moving from the engine vibrations.

It could be a bad connector at the sender for the water temp. I've had that happen before. The wire got fatigued, and it was almost broken off.

Max doesn't visit this site very often. Reach out to him at the Resurrected Classics website.

I don't have that relay harness, just the stock harness for that circuit. The only issues I experienced with some LEDs is that I had some type 1157 red LEDs fail so that they lit both "elements" at once. I chose a different brand that's in the list and experienced no problems since then. I first started using LEDs over 13 years ago and have no regrets. You may find corrosion in some or all of your side markers. I think that is part of the issue with the circuit overall.

From the factory wiring diagram: If you don't have a copy of the wiring diagram, download it from this site. You can find the Download section after you click on Resources at the top of the page.

It looks like someone installed a relay for the parking light circuit. See if you can hear the relay click when you turn on the parking lights.

In the spirit of @siteunseen, I had to search. One of the earliest mentions of the drain hole that I could find was by @Zs-ondabrainin 2008.

And here is a reproduction grommet if you still have the electric antenna: https://www.zeddsaver.com/products/datsun-z-antenna-drain-grommet

I saw it posted either here or at Zcar.com many years ago. I think I installed a body plug there when I was replacing the bumpers on my 260Z.

And just in case, here's an out-in-left-field issue I had to deal with a few years back when I lost my lights:

There is a problem with the 73-76 cars, and the 77-78 cars are only marginally better. The 20A fuse is too big to protect the wiring, especially with all of the connectors. The weakest connector is the 9-pin connector between the combo switch and dash harness. (The connector is different in the 77-78, but I've seen the problem there, too.) It will overheat with too much current flowing through it. Here is an example of a damaged one that I happen to have handy. The green wires you see are the ones for the parking light circuit. I hope the damage is obvious. The connection got so hot, the plastic started to melt. A solution: Replace the connector. You can find it at http://www.vintageconnections.com/ You may want to buy the pin removal tools. No matter what, it's a PITA to de-pin the old connector IMHO. Replace the side markers and gauge lights with LEDs. If you replace the front and rear markers, you'll also need to change to electronic turn signal flasher relays. Note: You can't just buy any LED bulbs for the gauge lights. Another user on this site found polarity independent bulbs that fit well. I will attach a suggested list of LED bulbs. Change the fuse for the parking lights to 10A. The reason why this solution works is that the current draw through the circuit has been reduced. That reduces the heat through the connector. If there is a short in the circuit, the fuse will blow before there is too much current flowing through the vulnerable connector. LED bulb list.txt

Forgot one hole: There's a drain hole for the power antenna. It's near the exhaust.